Inhibition of pulp and paper yellowing using nitroxides, hydroxylamines and other coadditives

ABSTRACT

Pulps or papers, especially chemimechanical or thermomechanical pulps or papers, which still contain lignin, have enhanced resistance to yellowing when they contain an effective stabilizing amount of a hindered amine compound which preferably is a nitroxide, a hydroxylamine or an ammonium salt thereof. This performance is often further enhanced by the presence of one or more coadditives selected from the group consisting of the UV absorbers, the polymeric inhibitors, the nitrones, the fluorescent whitening agents, metal chelating agents, sulfur containing stabilizers, metal salts and diene compounds. Combinations of nitroxides, hydroxylamines or their salts, benzotriazole or benzophenone UV absorbers and a metal chelating agent are particularly effective. Selected derivatives of 1-oxyl-2,2,6,6-tetramethyl-piperidin-4-ol and selected hydroxylamine salts are novel compounds and are surprisingly effective for this purpose.

This application is a divisional of application Ser. No. 09/119,567,filed Jul. 20, 1998, now U.S. Pat. No. 6,254,724, which applicationclaims the benefit under 35 USC 119(e) of U.S. provisional applicationNos. 60/053,489 and 60/054,968, filed on Jul. 23, 1997 and on Aug. 7,1997 respectively.

The instant invention pertains to a method for preventing the loss ofbrightness and for enhancing resistance to yellowing in pulp or paperwhich still contains lignin by the addition of nitroxides,hydroxylamines or their salts and other coadditives. The instantinvention also pertains to novel compounds which are selectedderivatives of 1-oxyl-2,2,6,6-tetramethyl-piperidin-4-ol or which aretheir hydroxylamine salts.

BACKGROUND OF THE INVENTION

High-yield and ultra-high yield wood pulps undergo rapid light-induceddiscoloration, particularly when they are exposed to near ultravioletlight (wave lengths 300-400 nm) in indoor fluorescent light anddaylight. This characteristic restricts their use to short-life,low-value paper products. High-yield and ultra-high yield wood pulps canbe bleached to a high level of whiteness. If this whiteness could bestabilized against discoloration, these bleached high-yield pulps coulddisplace significant amounts of more expensive fully-bleached, low-yieldchemical pulps.

This discoloration is ascribed to the substantial lignin content ofhigh-yield pulps totally about 20-30% by mass. Phenoxy radicals are thekey intermediates in the reaction mechanism. Several light-inducedreactions have been proposed to account for their formation such asabstraction of a hydrogen atom from phenolic groups, cleavage of thearyl ether bond of phenacyl aryl ether groups, or breakdown of ketylradicals formed from saturated aryl-glycerol β-aryl ether structures inlignin. The phenoxy radicals are oxidized by other oxygen-centeredradicals (alkoxy, peroxy, hydroxy and perhydroxy) to form yellowchromophores. (C. Heitner in “Photochemistry of LignocellulosicMaterials”, C. Heitner, J. C. Scaiano, eds,: ACS Sym. Ser. 531, 1-25(1993).)

I. E. Arakin et al., Khymiya drevesiny (Chemistry of Wood), 1982, No. 2,114 and A. D. Sergeev et al., ibid, 1984, No. 5, 20 disclosed that theuse of iminoxyl radicals such as TEMPO(1-oxyl-2,2,6,6-tetramethylpiperidine) is useful in the delignificationof wood using the one-stage oxygen-soda (alkaline) process, but made nomention or suggestion of any activity provided by TEMPO on preventinglight-induced discoloration of paper or pulp made from such treatedwood.

EP 717,143 and WO 97/36041 describe a multicomponent system forchanging, reducing or bleaching lignin and lignin-containing materialswhich comprise a oxidation catalyst, and a N-hydroxyl mediator compoundsuch as a N-hydroxyphthalimide or a dialkylhydroxylamine. Thesereferences are aimed at the delignification of wood. There is no mentionor suggestion of any activity provided by the N-hydroxyl compounds inpreventing the light-induced discoloration of paper or pulp made fromsuch treated wood.

V. I. Khodyrev et al., Vysokomol soyed, A29, No. 3, 616 (1987) [PolymerSci. U.S.S.R., 29, No. 3, 688 (1987)] show that the photoinitiatedoxidation by oxygen causes weathering of cellulosic textile materialssuch as flax or cotton. The UV absorbers offer no protection, and areactually detrimental. The authors noted that the stable nitroxyl radical1-oxyl-2,2,6,6-tetra-methyl-4-hydroxypiperidine interacts with alkylradicals in the cellulose to afford its salubrious stabilizing activity.There is no suggestion by the authors that this stabilizing activitycould be applied successfully in lignin-containing pulp and/or papermade therefrom.

M-K. Syker et al., J. Assn. Paper Pulp Tech, 29, 135 (1990) show thatselected metal salts such as magnesium sulfate and lower alkanoic acidsinhibit color reversion in bleached pulp.

P. Fornier de Violet et al., Cellulose Chem. Tech., 24, 225 (1990) showthat the use of UV absorbers and hydrogen donor agents such as thiols,ascorbic acid, etc. help prevent the photoinduced discoloration ofhydrogen peroxide bleached wood pulp, but that chain breakers such ashindered phenols and hindered amines (having >N—H or >N—CH₂— moieties)had no or even a detrimental effect on preventing photoinduceddiscoloration.

R. Agnemo et al., Holzforschung (1991), 45 (Suppl), 101, confirmed thatfree hydroxyl radicals plus lignin lead to undesirable photoyellowing inpulp and paper.

S. Omori et al., J. Assn. Paper Pulp Tech, 48, 1388 (1993) describes theeffect of antioxidants and UV absorbers on light reversion and concludesthat the combination of an antioxidant and UV absorber prevents colorreversion and has a synergistic effect in that activity.

M. Paulsson et al., Nordic Pulp Pap. Res. J., (1995), 10 (1), 62-67,show that efficient photostabilization of unbleached paper or hydrogenperoxide bleached TMP pulp can be achieved by acetylation.

There have been a number of different approaches proposed to inhibitingthe yellowing of mechanical pulps. These include: radical scavengers andantioxidants; UV screens; elimination of chromophores after theirformation; chemical modification of lignin by alkylation or acetylation;polymeric inhibitors; and two types of coadditives used in combination.Z-H. Wu et al., Holzforschung, 48, (1994), 400 discuss the use ofradical scavengers like phenyl-N-tert-butylnitrone to reduce theformation of chromophores during mechanical pulping and give a morelight-stable pulp.

C. Heitner, “Chemistry of Brightness Reversion and It Control, Chapter5”, in Pulp Bleaching-Principles and Practice, C. W. Dence, D. W. Reeve,eds., TAPPI Press, Atlanta, 1996, pp 183-211, summarizes the state ofthe art in the thermal and light-induced yellowing of lignin-containingpulps such as thermomechanical (TMP) and chemithermomechical (CTMP)pulps, showing the seriousness of these undesirable effects discussesgenerally the then current prior art methods used to attack thisproblem. These include bleaching, the use of phosphites, UV absorbers,polyalkylene glycols and free radical scavengers such as ascorbic acid,thiols, thioethers, dienes and aliphatic aldehydes and chelating agentssuch as ethylene-diaminetetraacetic acid (EDTA). The author concludedthat, although much progress had been made, much still remains to bedone before a successful and practical solution to this loss ofbrightness and undesirable yellowing of lignin-containing pulp and/orpaper is found.

The instant invention described in detail below provides such a solutionwhere the use of selected hindered amine nitroxides, hindered aminehydroxylamines or their salts in combination with selected UV absorbersand metal chelating agents is seen to prevent loss of brightness and toenhance resistance to yellowing in pulp or paper still containinglignin.

DETAILED DESCRIPTION OF THE INVENTION

The addition of hydroxylamines or nitroxide free radicals to high-yieldpulp paper either alone or in combinations with UV absorbers, metalchelating agents, fluorescent whitening agents and/or stabilizingpolymers effectively achieves light and thermal stability which issimilar to that found in papers made from kraft pulps.

Hydroxylamines and nitroxides are known to be efficient free radicaltraps and may limit the production of o-quinones; UV absorbers limitphotochemistry in the underlying substrate to which they are applied,and ultimately reduce the production of free radicals. UV absorbers andnitroxides are each effective at stemming some of the free radicalchemistry leading to paper yellowing when used singly. However, whenthey are used together, hydroxylamines or nitroxides and UV absorberscan effectively stop photochemical yellowing of lignin containing paperswhich are exposed 24 hours a day under ambient fluorecent lightingconditions for at least 200 days. Both of these types of stabilizersshow enhanced inhibiting activity when combined with a metal chelatingagent such diethylenetriaminepentaacetic acid, or polymeric inhibitorssuch as polyethylene glycol.

More particularly the instant invention pertains to a composition havingreduced loss of brightness and enhanced resistance to yellowing whichcomprises

(a) a pulp or paper which still contains lignin, and

(b) an effective stabilizing amount of a hindered amine compound offormula I or II

where

G₁ and G₂ are independently alkyl of 1 to 4 carbon atoms or are togetherpentamethylene,

Z₁ and Z₂ are each methyl, or Z₁ and Z₂ together form a linking moietywhich may additionally be substituted by an ester, ether, hydroxy,cyanohydrin, amide, amino, carboxy or urethane group,

E is oxyl, hydroxyl, hydrogen, alkyl, alkyl substituted by hydroxyl, oxoor carboxy or interrupted by oxygen or carboxy alkenyl, alkynyl,cycloalkyl, cycloalkenyl, bicycloalkyl, alkoxy, alkoxy substituted byhydroxyl, oxo or carboxy or interrupted by oxygen or carboxy,cycloalkoxy, alkenyloxy, aralkyl, aralkoxy, acyl, R(C═O)O—, RO(C═O)O—,RN(C═O)O— or chloro, where R is an aliphatic or aromatic moiety,

X is an inorganic or organic anion, such as phosphate, carbonate,bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate,sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate,acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, malate,mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate ofethylenediaminetetraacetic acid or of diethylenetriaminepentaaceticacid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonateor an arylsulfonate, and

where the total charge of cations h is equal to the total charge ofanions j, and with the proviso that the compound of formula I is notbis(2,2,6,6-tetramethylpiperidin-4-yl)sebacate or the polycondensationproduct of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidineand succinic acid.

Preferably, the compositions are those where in the compound ofcomponent (b), E is oxyl, hydroxyl, alkenyloxy, aralkoxy, alkyloxy oralkyl substituted by oxo or interrupted by carboxy, especially wherein Eis oxyl or hydroxy; most especially wherein E is hydroxy.

Most preferably, X is chloride, bisulfite, bisulfate, sulfate,phosphate, nitrate, acetate, citrate or carboxylate ofethylenediaminetetraacetic acid or of diethylenetriaminepentaaceticacid; most especially wherein X is bisulfate or citrate.

Preferably, the hindered amine compounds of component (b) are those offormulas A to EE and A* to EE*

wherein

E is oxyl, hydroxyl, hydrogen, alkyl of 1 to 18 carbon atoms, alkyl of 2to 12 carbon atoms substituted by one to three hydroxyl or said alkylinterrupted by one to four oxygen atoms, or said alkyl both substitutedby said hydroxyl groups and interrupted by said oxygen atoms, alkenyl of2 to 18 carbon atoms, alkynyl of 2 to 12 carbon atoms, cycloalkyl of 5to 12 carbon atoms, cycloalkenyl of 5 to 12 carbon atoms, bicycloalkylof 6 to 10 carbon atoms, alkoxy of 1 to 18 carbon atoms, alkoxy of 2 to12 carbon atoms substituted by one to three hydroxyl groups or saidalkoxy interrupted by one to four oxygen atoms or said alkoxysubstituted by —COOZ where Z is hydrogen or alkyl of 1 to 4 carbonatoms, cycloalkoxy of 5 to 12 carbon atoms, alkenyloxy of 2 to 18 carbonatoms, aralkyl of 7 to 15 carbon atoms, aralkoxy of 7 to 15 carbonatoms, alkanoyl of 2 to 12 carbon atoms, alkenoyl of 2 to 12 carbonatoms, benzoyl, or R(C═O)O—, RO(C═O)O—, RN(C═O)O—, where R is alkyl of 1to 6 carbon atoms or phenyl,

R is hydrogen or methyl,

in formula A and A*,

n is 1 or 2,

when n is 1,

R₁ is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2-18 carbonatoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atoms interrupted byone to twenty oxygen atoms, said alkyl substituted by one to tenhydroxyl groups or both interrupted by said oxygen atoms and substitutedby said hydroxyl groups, or

R₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by—COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, orwhere Z is said alkyl substituted by —(COO⁻⁾ _(n)M^(n+) where n is 1-3and M is a metal ion from the 1st, 2nd or 3rd group of the periodictable or is Zn, Cu, Ni or Co, or M is a group N^(n+)(R₂)₄ where R₂ isalkyl of 1 to 8 carbon atoms or benzyl,

when n is 2,

R₁ is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbonatoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by oneto twenty oxygen atoms, substituted by one to ten hydroxyl groups orboth interrupted by said oxygen atoms and substituted by said hydroxylgroups,

in formula B and B*,

m is 1 to 4,

when m is 1,

R₂ is alkyl of 1 to 18 carbon atoms, alkyl of 3 to 18 carbon atomsinterrupted by —COO—, or R₂ is —CH₂(OCH₂CH₂)_(n)OCH₃ where n is 1 to 12,or

R₂ is cycloalkyl of 5 to 12 carbon atoms, aryl of 6 to 12 carbon atoms,or said aryl substituted by one to four alkyl groups of 1 to 4 carbonatoms, or

R₂ is —NHR₃ where R₃ is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5to 12 carbon atoms, aryl of 6 to 12 carbon atoms, or said arylsubstituted by one to four alkyl of 1 to 4 carbon atoms, or

R₂ is —N(R₃)₂ where R₃ is as defined above,

when m is 2,

R₂ is alkyl of 1 to 12 carbon atoms, alkenyl of 4 to 12 carbon atoms,xylyl, alkyl of 2 to 12 carbon atoms interrupted by —COO—, or R₂ is—CH₂(OCH₂CH₂)_(n)OCH₂— where n is 1 to 12, or

R₂ is cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15 carbonatoms or aryl of 6 to 12 carbon atoms, or

R₂ is —NHR₄NH— where R₄ is alkylene of 2 to 18 carbon atoms,cycloalkylene of 5 to 12 carbon atoms, aralkylene of 8 to 15 carbonatoms or arylene of 6 to 12 carbon atoms, or

R₂ is —N(R₃)R₄N(R₃)— where R₃ and R₄ are as defined above, or

R₂ is —CO— or —NH—CO—NH—,

when m is 3,

R₂ is alkanetriyl of 3 to 8 carbon atoms or benzenetriyl, or

when m is 4,

R₂ is alkanetetrayl of 5 to 8 carbon atoms or benzenetetrayl,

in formula C and C*,

R₁₀ is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12carbon atoms, aralkyl of 7 to 15 carbon atoms, alkanoyl of 2 to 18carbon atoms, alkenoyl of 3 to 5 carbon atoms or benzoyl,

x is 1 or 2,

when x is 1,

R₁₁ is hydrogen, alkyl of 1 to 18 carbon atoms, alkenyl of 2 to 18carbon atoms, propargyl, glycidyl, alkyl of 2 to 50 carbon atomsinterrupted by one to twenty oxygen atoms, said alkyl substituted by oneto ten hydroxyl groups or both interrupted by said oxygen atoms andsubstituted by said hydroxyl groups, or

R₁₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by—COOZ where Z is hydrogen, alkyl of 1 to 4 carbon atoms or phenyl, orwhere Z is said alkyl substituted by —(COO⁻)_(n)M^(n+) where n is 1-3and M is a metal ion from the 1st, 2nd or 3rd group of the periodictable or is Zn, Cu, Ni or Co, or M is a group N^(n+)(R₂)₄ where R₂ isalkyl of 1 to 8 carbon atoms or benzyl, or

when x is 2,

R₁₁ is alkylene of 1 to 12 carbon atoms, alkenylene of 4 to 12 carbonatoms, xylylene or alkylene of 1 to 50 carbon atoms interrupted by oneto twenty oxygen atoms, substituted by one to ten hydroxyl groups orboth interrupted by said oxygen atoms and substituted by said hydroxylgroups,

in formula D and D*,

R₁₀ is as defined above,

y is 1 to 4, and

R₁₂ is defined as R₂ above,

in formula E and E*,

k is 1 or 2,

when k is 1,

R₂₀ and R₂₁ are independently alkyl of 1 to 12 carbon atoms, alkenyl of2 to 12 carbon atoms or aralkyl of 7 to 15 carbon atoms, or R₂₀ is alsohydrogen, or

R₂₀ and R₂₁ together are alkylene of 2 to 8 carbon atoms or saidalkylene substituted by hydroxyl, or are acyloxy-alkylene of 4 to 22carbon atoms, or

when k is 2,

R₂₀ and R₂₁ are together (—CH₂)₂C(CH₂—)₂,

in formula F and F*,

R₃₀ is hydrogen, alkyl of 1 to 18 carbon atoms, benzyl, glycidyl, oralkoxyalkyl of 2 to 6 carbon atoms,

g is 1 or 2,

when g is 1, R₃₁ is defined as R₁ above when n is 1,

when g is 2, R₃₁ is defined as R₁ above when n is 2,

in formula G and G*,

Q₁ is —NR₄₁— or —O—,

E₁ is alkylene of 1 to 3 carbon atoms, or E₁ is —CH₂—CH(R₄₂)—O— whereR₄₂ is hydrogen, methyl or phenyl, or E₁ is —(CH₂)₃—NH— or E₁ is adirect bond,

R₄₀ is hydrogen or alkyl of 1 to 18 carbon atoms,

R₄₁ is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbonatoms, or R₄₁ is —CH₂—CH(R₄₂)—OH where R₄₂ is as defined above,

in formula H and H*,

p is1 or 2,

T₄ is as defined for R₁₁ when x is 1 or 2,

M and Y are independently methylene or carbonyl, preferably M ismethylene and Y is carbonyl,

in formula I and I*,

this formula denotes a recurring structural unit of a polymer where T₁is ethylene or 1,2-propylene or is the repeating structural unit derivedfrom an alpha-olefin copolymer with an alkyl acrylate or methacrylate,and where

q is 2to 100,

Q₁ is —N(R₄₁)— or —O— where R₄₁ is as defined above,

in formula J and J*,

r is 1 or 2,

T₇ is as defined for R₁ when n is 1 or 2 in formula A,

preferably T₇ is octamethylene when r is 2,

in formula L and L*,

u is 1 or 2,

T₁₃ is as defined for R₁ when n is 1 or 2 in formula A, with the provisothat T₁₃ is not hydrogen when u is 1,

in formula M and M*,

E₁ and E₂, being different, each are —CO— or —N(E₅)— where E₅ ishydrogen, alkyl of 1 to 12 carbon atoms or alkoxycarbonylalkyl of 4 to22 carbon atoms, preferably E₁ is —CO— and E₂ is —N(E₅)—,

E₃ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl, saidphenyl or said naphthyl substituted by chlorine or by alkyl of 1 to 4carbon atoms, or phenylalkyl of 7 to 12 carbon atoms, or saidphenylalkyl substituted by alkyl of 1 to 4 carbon atoms,

E₄ is hydrogen, alkyl of 1 to 30 carbon atoms, phenyl, naphthyl orphenylalkyl of 7 to 12 carbon atoms, or

E₃ and E₄ together are polymethylene of 4 to 17 carbon atoms, or saidpolymethylene substituted by one to four alkyl of 1 to 4 carbon atoms,preferably methyl,

in formula N and N*,

R₁ is as defined for R₁ in formula A when n is 1,

G₃ is a direct bond, alkylene of 1 to 12 carbon atoms, phenylene or—NH—G₁—NH— where G₁ is alkylene of 1 to 12 carbon atoms,

in formula O and O*,

R₁₀ is as defined for R₁₀ in formula C,

in formula P and P*,

E₆ is an aliphtic or aromatic tetravalent radical, preferablyneopentanetetrayl or benzenetetrayl,

in formula T and T*,

R₅₁ is hydrogen, alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 12carbon atoms, or aryl of 6 to 10 carbon atoms,

R₅₂ is hydrogen or alkyl of 1 to 18 carbon atoms, or

R₅₁ and R₅₂ together of alkylene of 4 to 8 carbon atoms,

f is 1 or 2,

when f is 1,

R₅₀ is as defined for R₁₁ in formula C when x is 1, or R₅₀ is—(CH₂)_(z)COOR₅₄ where z is 1 to 4 and R₅₄ is hydrogen or alkyl of 1 to18 carbon atoms, or R₅₄ is a metal ion from the 1st, 2nd or 3rd group ofthe periodic table or a group —N(R₅₅)₄ where R₅₅ is hydrogen, alkyl of 1to 12 carbon atoms or benzyl,

when f is 2, R₅₀ is as defined for R₁₁ in formula C when x is 2,

in formula U and U*,

R₅₃, R₅₄, R₅₅ and R₅₆ are independently alkyl of 1 to 4 carbon atoms orare together pentamethylene.

in formula V and V*,

R₅₇, R₅₈, R₅₉ and R₆₀ are independently alkyl of 1 to 4 carbon atoms orare together pentamethylene.

in formula W and W*,

R₆₁, R₆₂, R₆₃ and R₆₄ are independently alkyl of 1 to 4 carbon atoms orare together pentamethylene,

R₆₅ is alkyl of 1 to 5 carbon atoms,

M is hydrogen or oxygen,

wherein in formulas X to CC and X* to CC*

n is 2 to 3,

G₁ is hydrogen, methyl, ethyl, butyl or benzyl,

m is 1 to 4,

x is 1 to 4,

when x is 1, R₁ and R₂ are independently alkyl of 1 to 18 carbon atoms,said alkyl interrupted by one to five oxygen atoms, said alkylsubstituted by 1 to 5 hydroxyl groups or said alkyl both interrupted bysaid oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10carbon atoms or said aryl substituted by one to three alkyl of 1 to 8carbon atoms, or R₁ is also hydrogen,

or R₁ and R₂ are together tetramethylene, pentamethylene, hexamethyleneor 3-oxapentamethylene,

when x is 2,

R₁ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orsaid alkyl both interrupted by one or two oxygen atoms and substitutedby a hydroxyl group,

R₂ is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by oneto five oxygen atoms, said alkylene substituted by 1 to 5 hydroxylgroups or said alkylene both interrupted by said oxygen atoms andsubstituted by said hydroxyl groups; o-, m- or p-phenylene or saidphenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or

R₂ is —(CH₂)_(k)O[(CH₂)_(k)O]_(h)(CH₂)_(k)— where k is 2 to 4 and h is 1to 40, or

R₁ and R₂ together with the two N atoms to which they are attached arepiperazin-1,4-diyl,

when x is 3,

R₁ is hydrogen,

R₂ is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,

when x is 4,

R₁ is hydrogen,

R₂ is alkylene of 6 to 12 carbon atoms interrupted by two nitrogenatoms,

R₃ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orboth interrupted by one or two oxygen atoms and substituted by ahydroxyl group,

p is 2or 3, and

Q is an alkali metal salt, ammonium or N⁺(G₁)₄,

in formula DD and DD*

m is 2 or 3,

when m is 2, G is —(CH₂CHR—O)_(r)CH₂CHR—, where r is 0 to 3, and R ishydrogen or methyl, and

when m is 3, G is glyceryl,

in formula EE and EE*

G₂ is —CN, —CONH₂ or —COOG₃ where G₃ is hydrogen, alkyl of 1 to 18carbon atoms or phenyl,

X is an inorganic or organic anion, such as phosphate, carbonate,bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate,sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate,acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, malate,mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate ofethylenediaminetetraacetic acid or of diethylenetriaminepentaaceticacid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonateor an arylsulfonate, and

where the total charge of cations h is equal to the total charge ofanions j, and with the proviso thatbis(2,2,6,6-tetramethylpiperidin-4-yl)sebacate or the polycondensationproduct of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidineand succinic acid are excluded.

Most preferably, the compounds of component (b) are those of formulas A,A*, B, B*, C, C*, D, D*, Q, Q*, R, R*, S, S*, X, X*, Y, Y*, Z and Z*,

where E is oxyl or hydroxyl,

R is hydrogen,

in formula A and A*

n is 1 or 2,

when n is 1,

R₁ is hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl of 2-6 carbonatoms, propargyl, glycidyl, alkyl of 2 to 20 carbon atoms interrupted byone to ten oxygen atoms, said alkyl substituted by one to five hydroxylgroups or both interrupted by said oxygen atoms and substituted by saidhydroxyl groups, or

R₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or by—COOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,

when n is 2,

R₁ is alkylene of 1 to 8 carbon atoms, alkenylene of 4 to 8 carbonatoms, alkylene of 1 to 20 carbon atoms interrupted by one to ten oxygenatoms, substituted by one to five hydroxyl groups or both interrupted bysaid oxygen atoms and substituted by said hydroxyl groups,

in formula B and B*

m is 1 or 2

when m is 1,

R₂ is alkyl of 1 to 4 carbon atoms or R₂ is CH₂(OCH₂CH₂)_(n)OCH₃ where nis 1 to 12, or

R₂ is phenyl, or said phenyl substituted by one to three methyl groups,

R₂ is —NHR₃ where R₃ is alkyl of 1 to 4 carbon atoms or phenyl, or saidphenyl substituted by one or two methyl groups,

when m is 2,

R is alkyl of 1 to 8 carbon atoms, alkenyl of 4 to 8 carbon atoms, or R₂is —CH₂(OCH₂CH₂)_(n)OCH₂— where n is 1 to 12,

R₂ is NHR₄NH where R₄ is of 2 to 6 carbon atoms, aralkylene of 8 to 15carbon atoms or arylene of 6 to 12 carbon atoms,

R₂ is —CO— or —NHCONH,

in formula C and C*,

R₁₀ is hydrogen or, alkanoyl of 1 to 3 carbon atoms,

x is 1 or 2,

when x is 1,

R₁₁ is hydrogen, alkyl of 1 to 6 carbon atoms or glycidyl,

R₁₁ is alkyl of 1 to 4 carbon atoms substituted by a carboxy group or byCOOZ where Z is hydrogen or alkyl of 1 to 4 carbon atoms,

when x is 2,

R₁₁ is alkylene of 1 to 6 carbon atoms,

in formula D and D*,

R₁₀ is hydrogen,

y is 1 or 2,

R₁₂ is defined as R₂ above,

in formula Z and Z*,

x is 1 or 2,

when x is 1,

R₁ and R₂ are independently alkyl of 1 to 4 carbon atoms,

or R₁ and R₂ are together tetramethylene, or pentamethylene,

R₂ is hydrogen or alkyl of 1 to 4 carbon atoms, said alkyl groupsubstituted by a hydroxyl group,

when x is 2,

R₁ is hydrogen, alkyl of 1 to 4 carbon atoms, said alkyl substituted bya hydroxyl group,

R₂ is alkylene of 2 to 6 carbon atoms,

R₃ is as defined above.

Especially preferred, the compounds of component (b) are those offormulas A, A*, B, B*, C, C*, D, D*, Q, Q*, R and R*,

where E is oxyl or hydroxyl,

R is hydrogen,

in formula A and A*,

h is 1,

R₁ is hydrogen, alkyl of 1 to 4 carbon atoms, glycidyl, alkyl of 2 to 4carbon atoms interrupted by one or two oxygen atoms, said alkylsubstituted by one or two hydroxyl groups or both interrupted by saidoxygen atoms and substituted by said hydroxyl groups, or

R₁ is alkyl of 1 to 4 carbon atoms substituted by —COOZ where Z ishydrogen or alkyl of 1 to 4 carbon atoms,

in formula B and B*,

m is 1 or 2,

R₂ is alkyl of 1 to 4 carbon atoms or R₂ is CH₂(OCH₂CH₂)_(n)OCH₃ where nis 1 to 4,

when m is 2,

R is alkyl of 1 to 8 carbon atoms,

in formula C and C*,

R₁₀ is hydrogen or alkanoyl of 1 or 2 carbon atoms,

x is 1 or 2,

when x is 1,

R₁₁ is hydrogen, alkyl of 1 to 4 carbon atoms or glycidyl,

R₁₁ is alkyl of 1 to 4 carbon atoms substituted by COOZ where Z ishydrogen or alkyl of 1 to 4 carbon atoms,

when x is 2,

R₁₁ is alkylene of 1 to 6 carbon atoms,

in formula D and D*,

R₁₀ is hydrogen,

y is 1 or 2,

R₁₂ is defined as R₂ above.

More particularly, the hindered amine compound is

(a) bis(1-oxyl-2,2-6-6-tetramethylpiperidin-4-yl)sebacate;

(b) bis(1-hydroxy-2,2-6-6-tetramethylpiperidin-4-yl)sebacate;

(c) 1-hydroxy-2,2-6-6-tetramethylpiperidinium-4-yl acetate;

(d) 1-oxyl-2,2,6,6-tetramethyl-4-acetamidopiperidine;

(e) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidine;

(f) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium bisulfate;

(g) 1-oxyl-2,2,6,6-tetramethyl-4-oxo-piperidine;

(h) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine;

(i) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium acetate;

(j) 1-oxyl-2,2,6,6-tetramethyl-4-methoxy-piperidine;

(k) 1-hydroxy-2,2,6,6-tetramethyl-4-methoxy-piperidine;

(l) 1-hydroxyl-2,2,6,6-tetramethyl-4-methoxy-piperidinium acetate;

(m) 1-oxyl-2,2,6,6-tetramethyl-4-acetoxypiperidine;

(n) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidine;

(o) 1-oxyl-2,2,6,6-tetramethyl-4-propoxy-piperidine;

(p) 1-hydroxy-2,2,6,6-tetramethyl-4-propoxy-piperidinium acetate;

(q) 1-oxyl-2,2,6,6-tetramethyl-4-propoxy-piperidine;

(r) 1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxapentoxy)piperidine;

(s) 1-hydroxy-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxapentoxy)piperidiniumacetate;

(t) 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine;

(u) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;

(v) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium chloride;

(w) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium acetate;

(x) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium bisulfate;

(y) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;

(z) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

(aa) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate.

(bb)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)ethylenediaminetetraacetate;

(cc)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)ethylenediaminetetraacetate;

(dd)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)ethylenediaminetetraacetate;

(ee)penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)diethylenetriaminepentaacetate;

(ff)penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)diethylenetriaminepentaacetate;

(gg)penta(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)diethylenetriaminepentaacetate;

(hh)tri(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)nitrilotriacetate;

(ii)tri(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)nitrilotriacetate;

(jj)tri(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)nitrilotriacetate;

(kk)penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)diethylenetriaminepentamethylenephosphonate;

(ll)penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)diethylenetriaminepentamethylenephosphonate;

(mm)penta(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)diethylenetriaminepentamethylenephosphonate.

Most especially, the hindered amine compound is

(a) 1-oxyl-2,2,6,6-tetramethyl4-hydroxypiperidine;

(b) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;

(c) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium chloride;

(d) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium acetate;

(e) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium bisulfate;

(f) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;

(g) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

(h) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

(i)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)ethylenediaminetetraacetate;

(j)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)ethylenediaminetetraacetate;

(k)tetra(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)ethylenediaminetetraacetate;

(l)penta(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)diethylenetriaminepentaacetate;

(m)penta(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)diethylenetriaminepentaacetate;

(n)penta(1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinium)diethylenetriaminepentaacetate.

The instant compounds may additionally include an effective stabilizingamount of at least one stabilizer selected from the group consisting ofthe UV absorbers, the polymeric inhibitors, the sulfur containinginhibitors, the phosphorus containing compounds, the nitrones, thebenzofuran-2-ones and the hydroxylamines.

The compositions which also include a UV absorber are especiallypreferred. The UV absorber is selected from group consisting of thebenzotriazoles, the s-triazines, the benzophenones, theα-cyanoacrylates, the oxanilides, the benzoxazinones, the benzoates andthe α-alkyl cinnamates.

Preferably, the UV absorber is a benzotriazole, an s-triazine or abenzophenone, most especially a benzotriazole UV absorber orbenzophenone UV absorber.

Typical and useful UV absorbers are, for example,

(a) 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;

(b) 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;

(c) 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;

(d) 2-(2-hydroxy-3,5-di-α-cumylphenyl)-2H-benzotriazole;

(e) 2-(2-hydroxy-3-α-cumyl-5-tert-octylphenyl)-2H-benzotriazole;

(f) 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole;

(g)3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonicacid monosodium salt;

(h) 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acidand sodium salt;

(i) 12-hydroxy-3,6,9-trioxadodecyl3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;

(j) octyl3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;

(k)4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine (* is mixture of C₁₂₋₁₄oxy isomers);

(l)4,6-bis(2,4-dimethylphenyl)-2-(4-octyloxy-2-hydroxyphenyl)-s-triazine;

(m) 2,4-dihydroxybenzophenone;

(n) 2,2′,4,4′-tetrahydroxy-5,5′-disulfobenzophenone, disodium salt;

(o) 2-hydroxy-4-octyloxybenzophenone;

(p) 2-hydroxy-4-dodecyloxybenzophenone;

(q) 2,4-dihydroxybenzophenone;

(r) 2,2′,4,4′-tetrahydroxybenzophenone;

(s) 4-aminobenzoic acid;

(t) 2,3-dihydroxypropyl-4-aminobenzoic acid;

(u) 3-(4-imidazolyl)acrylic acid;

(v) 2-phenyl-5-benzimidazole sulfonic acid;

(w) N,N,N-trimethyl-α-(2-oxo-3-bornylidene)-p-toluidinium methylsulfate;

(x) 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, sodium salt;

(y)3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxy-N,N,N-trimethyl-1-propanaminiumchloride;

(z)3-[4-(2H-benzotriazol-2-yl)-3-hydroxyphenoxy]-2-hydroxy-N,N,N-trimethyl-1-propanaminium,chloride;

(aa) 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole.

Preferred UV absorbers are

(a)3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonicacid monosodium salt;

(b) 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acidand sodium salt;

(c) 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;

(d) 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;

(e)4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine (* is mixture of C₁₂₋₁₄oxy isomers);

(f) 12-hydroxy-3,6,9-trioxadodecyl3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;

(g) 2,4-dihydroxybenzophenone;

(h) 2,2′,4,4′-tetrahydroxy-5,5′-disulfobenzophenone, disodium salt;

(i) 2,2′,4,4′-tetrahydroxybenzophenone;

(j)3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxy-N,N,N-trimethyl-1-propanaminiumchloride;

(k)3-[4-(2H-benzotriazol-2-yl)-3-hydroxyphenoxy]-2-hydroxy-N,N,N-trimethyl-1-propanaminium,chloride;

(l) 5-benzoyl-4-hydroxy-2-methoxy-benzenesulfonic acid, sodium salt

(m) 2-(2-hydroxy-3-α-cumyl-5-tert-octylphenyl)-2H-benzotriazole.

Other preferred compositions are those which additionally contain ametal chelating agent, i.e. those that offer thermodynamic or kineticcontrol of metal ions. Examples kinetic controlling chelating agents arecitrates, keto acids, gluconates, heptagluconates, phosphates, andphosphonates. Examples of chelating agents that offer thermodynamiccontrol are the aminocarboxylic acid chelates. Well known andcommercially available members of this class includeethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaaceticacid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA),nitrilotriacetic acid (NTA) anddiethylenetriaminepentamethylenephosphonic acid (DTPMPA).

Still other preferred compositions are those which contain mixtures ofthermodynamic and kinetic controlling chelating agents are alsopreferred.

Still other preferred compositions are those which additionally containa polymeric inhibitor; preferably poly(ethylene glycol) (PEO),poly(propylene glycol) (PPO), poly(butylene glycol) (PTHF), poly(vinylpyrrolidone) (PVP) or thiol-capped poly(ethylene glycol) as well ascopolymers such as poly(ethylene/propylene glycol).

Still other preferred compositions are those which additional contain afluorescent whitening agent selected from a wide range of chemical typessuch as 4,4′-bis-(triazinylamino)-stilbene-2,2′-disulfonic acids,4,4′-bis-(triazol-2-yl)stilbene-2,2′-disulfonic acids,4,4′-dibenzofuranyl-biphenyls, 4,4′-(diphenyl)-stilbenes,4,4′-distyryl-biphenyls, 4-phenyl-4′-benzoxazolyl-stilbenes,stilbenyl-naphthotriazoles, 4-styryl-stilbenes, bis-(benzoxazol-2-yl)derivatives, bis-(benzimidazol-2-yl) derivatives, coumarins,pyrazolines, naphthalimides, triazinyl-pyrenes, 2-styryl-benzoxazole or-naphthoxazoles, benzimidazole-benzofurans or oxanilides.

Some preferred compositions contain a mixture of additional stabilizerssuch as a mixture of a UV absorber and polymeric inhibitor; or a mixtureof a UV absorber and a metal chelating agent; or a mixture of apolymeric inhibitor and a metal chelating agent; or a mixture of apolymeric inhibitor and a fluorescent whitening agent; or a mixture of afluorescent whitening agent and a metal chelating agent; or a mixture ofa UV absorber, metal chelating agent and a polymeric inhibitor; or amixture of fluorescent whitening agent, metal chelating agent andpolymeric inhibitor.

Preferably the compositions are those wherein the compound of formula Ior II is of low molecular weight or contains hydrophilic moietiesespecially cationic groups, is both of low molecular weight and containshydrophilic moieties.

The instant invention also pertains to a process for preventing the lossof brightness and for enhancing resistance to yellowing ofchemimechanical or thermomechanical pulp or paper which still containslignin, which comprises

treating said pulp or paper with an effective stabilizing amount of acompound of formula I or II, preferably a compound of formula A to EE orA* to EE* as described above.

Preferably the process is that where in the compound of formula A to EEor A* to EE*, E is oxyl or hydroxyl and most preferably E is hydroxyl.

The instant invention also pertains to new compounds of formula IV, V,VI, VII or VIII

wherein

n is 2 to 3,

G₁ is hydrogen, methyl, ethyl, butyl or benzyl,

X is an inorganic or organic anion, such as phosphate, carbonate,bicarbonate, nitrate, chloride, bromide, bisulfite, sulfite, bisulfate,sulfate, borate, formate, acetate, benzoate, citrate, oxalate, tartrate,acrylate, polyacrylate, fumarate, maleate, itaconate, glycolate, malate,mandelate, tiglate, ascorbate, polymethacrylate, a carboxylate ofethylenediaminetetraacetic acid or of diethylenetriaminepentaaceticacid, a diethylenetriaminepentamethylenephosphonate, an alkylsulfonateor an arylsulfonate,

m is 1 to 4,

x is 1 to 4,

when x is 1, R₁ and R₂ are independently alkyl of 1 to 18 carbon atoms,said alkyl interrupted by one to five oxygen atoms, said alkylsubstituted by 1 to 5 hydroxyl groups or said alkyl both interrupted bysaid oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10carbon atoms or said aryl substituted by one to three alkyl of 1 to 8carbon atoms, or R₁ is also hydrogen,

or R₁ and R₂ are together tetramethylene, pentamethylene, hexamethyleneor 3-oxapentamethylene,

when x is 2,

R₁ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orsaid alkyl both interrupted by one or two oxygen atoms and substitutedby a hydroxyl group,

R₂ is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by oneto five oxygen atoms, said alkylene substituted by 1 to 5 hydroxylgroups or said alkylene both interrupted by said oxygen atoms andsubstituted by said hydroxyl groups; o-, m- or p-phenylene or saidphenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or

R₂ is —(CH₂)_(k)O[(CH₂)_(k)O]_(h)(CH₂)_(k)— where k is 2 to 4 and h is 1to 40, or

R₁ and R₂ together with the two N atoms to which they are attached arepiperazin-1,4-diyl,

when x is 3,

R₁ is hydrogen,

R₂ is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,

when x is 4,

R₁ is hydrogen,

R₂ is alkylene of 6 to 12 carbon atoms interrupted by two nitrogenatoms,

R₃ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orboth interrupted by one or two oxygen atoms and substituted by ahydroxyl group,

p is 2 or 3, and

Q is an alkali metal salt, ammonium or N⁺(G₁)₄.

Preferably, in the compounds of formulas IV to VIII

n is 2; G₁ is hydrogen or methyl; X is chloro or bromo; x is 1 or 2, R₁and R₂ are independently alkyl of I to 8 carbon atoms, said alkylinterrupted by one or two oxygen atoms, said alkyl substituted by ahydroxyl group, or said alkyl both interrupted by one or two oxygenatoms and substituted by a hydroxyl group, or R₁ is hydrogen; or R₁ andR₂ together are 3-oxa-pentamethylene, R₃ is hydrogen or alkyl of 1 to 2carbon atoms, or said alkyl substituted by a hydroxyl group, p is 2, mis 1, and Q is Na⁺, NH₄ ⁺ or N(CH₃)₄ ⁺.

Typical compounds falling within the structures of formulas IV to VIIIand which are useful in this invention are:

(a)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxa-6-trimethylammmoniumhexyloxy)piperidinechloride;

(b)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-trimethylammoniumpropoxy)piperidinechloride;

(c)1-oxyl-2,2,6,6-tetramethyl-4-{2-hydroxy-3-[di(2-hydroxyethyl)amino]propoxy}piperidine;

(d)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-dimethylaminopropoxy)piperidine;

(e)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-diethylaminopropoxy)piperidine;

(f)N,N′-dimethyl-N,N′-bis-[3-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxy)-2-hydroxypropyl]hexamethylenediamine;

(g)N,N,N′,N′-tetramethyl-N,N′-bis-[3-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxy)-2-hydroxypropyl]-hexamethylenediammoniumdibromide;

(h)1-oxyl-2,2,6,6-tetramethyl-4-[2-hydroxy-3-(N,N-dimethyl-N-propylammonium)propoxy]piperidinechloride;

(i) sodium 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetate; or

(j) 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetic acid, cholineester.

The instant invention also pertains to novel hydroxylamine salts offormulae A*, D*, X*, Y*, Z*, M*, BB*, CC* and DD*,

wherein

R is hydrogen,

in formula A*

n is 1,

R₁ is hydrogen or alkyl of 1 to 4 carbon atoms, preferably hydrogen,

in formula D*

y is 1,

R₁₀ is hydrogen or methyl, preferably hydrogen,

R₁₂ is alkyl of 1 to 4 carbon atoms, preferably methyl,

X is phosphate, carbonate, bicarbonate, nitrate, chloride, bromide,bisulfite, sulfite, bisulfate, sulfate, borate, formate, acetate,benzoate, citrate, oxalate, tartrate, acrylate, polyacrylate, fumarate,maleate, itaconate, glycolate, malate, mandelate, tiglate, ascorbate,polymethacrylate, a carboxylate of ethylenediaminetetraacetic acid or ofdiethylenetriaminepentaacetic acid, adiethylenetriaminepentamethylenephosphonate, an alkylsulfonate or anarylsulfonate,

where the total charge of cations h is equal to the total charge ofanions j,

wherein in formulas X* to DD*

n is 2 to 3,

G₁ is hydrogen, methyl, ethyl, butyl or benzyl,

m is 1 to 4,

x is 1 to 4,

when x is 1, R₁ and R₂ are independently alkyl of 1 to 18 carbon atoms,said alkyl interrupted by one to five oxygen atoms, said alkylsubstituted by 1 to 5 hydroxyl groups or said alkyl both interrupted bysaid oxygen atoms and substituted by said hydroxyl groups; cycloalkyl of5 to 12 carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10carbon atoms or said aryl substituted by one to three alkyl of 1 to 8carbon atoms, or R₁ is also hydrogen,

or R₁ and R₂ are together tetramethylene, pentamethylene, hexamethyleneor 3-oxapentamethylene,

when x is 2,

R₁ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orsaid alkyl both interrupted by one or two oxygen atoms and substitutedby a hydroxyl group,

R₂ is alkylene of 2 to 18 carbon atoms, said alkylene interrupted by oneto five oxygen atoms, said alkylene substituted by 1 to 5 hydroxylgroups or said alkylene both interrupted by said oxygen atoms andsubstituted by said hydroxyl groups; o-, m- or p-phenylene or saidphenylene substituted by one or two alkyl of 1 to 4 carbon atoms, or

R₂ is —(CH₂)_(k)O[(CH₂)_(k)O]_(h)(CH₂)_(k)— where k is 2 to 4 and h is 1to 40, or

R₁ and R₂ together with the two N atoms to which they are attached arepiperazin-1,4-diyl,

when x is 3,

R₁ is hydrogen,

R₂ is alkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom,

when x is 4,

R₁ is hydrogen,

R₂ is alkylene of 6 to 12 carbon atoms interrupted by two nitrogenatoms,

R₃ is hydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted byone or two oxygen atoms, said alkyl substituted by a hydroxyl group, orboth interrupted by one or two oxygen atoms and substituted by ahydroxyl group,

p is 2 or 3, and

Q is an alkali metal salt, ammonium or N⁺(G₁)₄,

in formula DD and DD*

m is 2 or 3,

when m is 2, G is —(CH₂CHR—O)_(r)CH₂CHR—, where r is 0 to 3, and R ishydrogen or methyl, and

when m is 3, G is glyceryl,

with the proviso that in formula A* when R₁ is hydrogen, X is notchloride or bisulfate, and when in formula D* when R₁₀ is hydrogen andR₁₂ is methyl, X is not chloride or bisulfate.

Preferably, X is chloride, bisulfate, bisulfite, sulfate, nitrate,acetate, citrate or carboxylate of ethylenediaminetetraacetic acid ordiethylenetriaminepentaacetic acid; most preferably, X is bisulfate orcitrate.

Hydroxylamine salts of particular interest are

(a) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate;

(b) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

(c) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

(d) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA;

(e) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) DTPA;

(f) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) DTPA;

(g) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) DTPA;

(h) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) DTPA;

(i) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium EDTA;

(j) bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA;

(k) tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA;

(l) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA;

(m) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium citrate;

(n) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)citrate;

(o) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium)citrate;

(p) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium DTPA;

(q) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA;

(r) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA;

(s) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA;

(t) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA;

(u) 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium EDTA;

(v) bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA;

(w) tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA;

(x) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA;

(y) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium citrate;

(z) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)citrate;

(aa) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)citrate;

(bb) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium DTPA;

(cc) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) DTPA;

(dd) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) DTPA;

(ee) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;

(ff) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA;

(gg) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium EDTA;

(hh) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) EDTA;

(ii) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) EDTA;

(jj) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA;

(kk) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium citrate;

(ll) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)citrate;

(mm) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium)citrate;

(nn) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium DTPA;

(oo) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA;

(pp) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA;

(qq) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA;

(rr) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA;

(ss) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium EDTA;

(tt) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA;

(uu) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA or

(vv) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA.

Nitroxides, hydroxylamines and their salts alone or in combination withUV absorbers are also effective in improving the resistance to yellowingof mechanical pulps which have been modified by acylation, alkylation,treatment with sodium borohydride or hydrogenated.

The intermediates needed to make the instant compounds are largely itemsof commerce.

The effective stabilizing amounts of the hindered amine is 0.001 to 5%by weight based on the pulp or paper. Preferably, the effectivestabilizing amount is 0.005 to 2% by weight; preferably 0.01 to 1% byweight.

When a coadditive stabilizer is also present, the effective stabilizingamount of the coadditives is also 0.001 to 5% by weight based on thepulp or paper; preferably 0.005 to 2% by weight; most preferably 0.01 to2% by weight.

The instant inhibitor additive system can be added to pulp or paper at anumber of places during the manufacturing or processing operations.These include

a. on a pulp slurry in the latency chest;

b. on a pulp slurry in or after the bleaching stage in a storage,blending or transfer chest;

c. on pulp during or after bleaching, washing and dewatering followed bycylinder or flash drying;

d. before or after the cleaners;

e. before or after the fan pump to the paper machine headbox;

f. to the paper machine white water;

g. to the silo or save all;

h. in the press section using a size press, coater or spray bar;

i. in the drying section using a size press, coater or spray bar;

j. on the calender using a wafer box; and/or

k. on paper in an off-machine coater or size press.

Clearly, the precise location where the stabilizer additives should beadded will depend on the specific equipment involved, the exact processconditions being used and the like. In some cases, the additives may beadded at one or more locations for most effectiveness.

The following examples are for illustrative purposes only and are not tobe construed to limit the instant invention in any manner whatsoever.

Handsheet Treatment

All additives are applied by syringe-injecting the appropriate weight %of additive combination in either an aqueous solution when the additiveis water soluble, or a solution in 1:1 (ethanol/dioxane) onto bleachedthermomechanical pulp (BTMP) brightness squares (4 cm×4 cm). The clampedsheets are allowed to air dry for one day.

The brightness of the handsheets is recorded before and after treatmentby light exposure.

Accelerated testing is carried out by subjecting the treated sheets toaccelerated light induced yellowing in a fan-cooled light box containingeight fluorescent lamps with a spectral maximum output at 5700 Å with atotal output approximately 43 times greater than normal officefluorescent lamps. The lamps are only about ten inches away from thehandsheets being illuminated.

Ambient testing is carried out by placing the treated handsheets on adesk under normal cool-white fluorescent office lights at a nominaldistance of six feet.

In both case ISO brightness is tracked as a function of photolysis timeand converted to post color number (PC number) in the usual manner.(Giertz, Svensk Papperstidn, (1945) 48 (13), 317)

Post color (PC) number is defined as follows:

PC=[(k/s)_(after)−(k/s)_(before)]×100

k/s=(1−R _(inf))²/2R _(inf)

where k and s are the absorption and scattering coefficients,respectively, and R_(inf) is the value of ISO brightness.

The relationship between R_(inf) and the chromophore concentration isnon-linear, whereas, the PC number is roughly linearly related to theconcentraton of the chromophore in the sample.

Low PC numbers are desired as they indicate less yellowing.

When using the ambient test conditions untreated BTMP handsheets arecompared to Kraft handsheets, after 60 days the BTMP handsheets have aPC number which is about 10 while the Kraft paper has a PC number whichis 0.388742. The Kraft handsheets are clearly less yellow than untreatedBTMP handsheets after exposure to ambient light.

The incident light flux for the accelerated yellowing experiments(Examples 1-4) is 43 times greater than normal office fluorescent lampsas measured by the A. W. Speery SLM-110 digital light power meter. Thebrightness of the handsheets is tracked and compared to that ofuntreated sheets exposed in the same manner. The treated sheets exhibitsignificant resistance to yellowing as seen below.

Materials Used in the Examples

Compound A is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine;

Compound B is 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine;

Compound C is 1-oxyl-2,2,6,6-tetramethyl-4-acetamidopiperidine;

Compound D is 1-oxyl-2,2,6,6-tetramethylpiperidine TEMPO;

Compound E is bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate;

Compound F is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidiniumchloride;

Compound G is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidiniumbisulfate;

Compound H isbis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)sulfate;

Compound I is 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidiniumacetate;

Compound J ispentakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)diethylenetriaminepentaaceticacid;

Compound K is3-(4-benzyloxy-2,2,6,6-tetramethyl-piperidin-1-yloxy)-propionic acidmethyl ester (PAX-3008);

Compound L is3-(4-{4-[1-(2-methoxycarbonyl-ethoxy)-2,2,6,6-tetramethyl-piperidin-4-yloxymethyl]-benzyloxy}-2,2,6,6-tetramethyl-piperidin-1-yloxy)-propionicacid methyl ester (PAX-3036);

Compound M is 2,2-diethyl-malonic acidbis-(1-butylcarbamoyloxy-2,2,6,6-tetramethyl-piperidin-4-yl)ester(PAX-3123);

Compound N is acetic acid 4-hydroxy-2,2,6,6-tetramethyl-piperidin-1-ylester (PAX-3136);

Compound O is benzoic acid1-butoxycarbonyloxy-2,2,6,6-tetramethyl-piperidin-4-yl ester (PAX-3267);

Compound P is 2,2,6,6-tetramethyl-1-(1-phenyl-ethoxy)-piperidin-4-ol(PAX-3156)

Compound Q is 2,4-dihydroxybenzophenone;

Compound R is12-hydroxy-3,6,9-trioxadodecyl-3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate(Tinuvin® 1130);

Compound S is,3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonicacid monosodium salt (Cibafast® W);

Compound T is1-oxyl-2,2,6,6-tetramethyl-4-(2,3-dihydroxypropoxy)piperidine;

Compound U is 1-oxyl-2,2,6,6-tetramethyl-4-(carboxymethoxy)piperidine;

Compound V is3-oxyl-1,2,2,4,4-pentamethyl-3,4-dihydro-2.H.-imidazol-1-iummethylsulfate;

Compound W is3-(3-benzotriazol-2-yl-5-.tert.-butyl-4-hydroxy-phenyl)-propionic acidCG20-0568;

Compound X is polyethylene glycol of molecular weight 300 (PEO);

Compound Y is4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine(* is mixture of C₁₂₋₁₄oxy isomers) (Tinuvin® 400);

Compound Z is 2,2′-dihydroxy-4,4′-dimethoxy-5,5′-disulfobenzophenone,disodium salt (Uvinul® 3048);

Compound AA is 2,2′-dihydroxy-4,4′-dimethoxybenzophenone (Uvinul® 3049);

Compound BB is diethylenetriamine tetraacidic acid (DTPA);

Compound CC is 5,5-dimethyl-1-pyrroline N-oxide;

Compound DD is N-tert-butyl-α-phenylnitrone;

Compound EE is 1-oxyl-2,2,6,6-tetramethyl-4-oxo-piperidine;

Compound FF istris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)citrate;

Compound GG is dithiothreitol;

Compound HH is 1-thioglycerol;

Compound II is 2,2′-oxydiethanethiol;

Compound JJ is 2,2,6,6-tetramethyl-4-acetamidopiperidine;

Compound KK is UVINUL® 3000, 2,4-dihydroxybenzophenone;

Compound LL is Brightener 28;4,4′-bis[4-anilino-6-(bis(2-hydroxyethyl)amino-s-triazin-2-yl]amino-2,2′-stilbenedisulfonicacid, disodium salt;

TMHP is 2,2,6,6-tetramethyl-4-hydroxypiperidine.

EXAMPLE 1 Accelerated Yellowing with High Intensity Lamps

A BTMP sheet is treated with 0.5%-0.1% by weight of Compound A. Thesheets treated with Compound A exhibit substantial inhibition toyellowing compared to the untreated control sheet as seen by the PCnumbers.

Concentration Time in Days 0.5% 0.4% 0.3% 0.2% 0.1% Blank PC Number 1.01.63 1.51 1.56 1.67 2.13 5.51 2.1 3.05 2.94 3.12 3.35 4.2 9.97 3.0 4.174.09 4.37 4.76 5.92 13.14 4.0 5.35 5.26 5.56 6.01 6.82 15.85 5.0 6.286.35 6.76 7.24 8.97 18.07 6.1 7.43 7.52 7.87 8.54 10.42 20.4 7.0 8.468.66 9.10 9.88 12.09 23.63

Even levels as low as 0.1% by weight of Compound A show effectivestabilization effects.

EXAMPLE 2 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of various hydroxylaminecompounds by the procedure of Example 1.

1-hydroxy-2,2,6,6-tetramethyl-1,2,3,6-tetrahydro-pyridine;

1-hydroxy-2,2,6,6-tetramethyl-4-methoxypiperidine;

1-hydroxy-2,2,6,6-tetramethyl-4-ethoxypiperidine;

1-hydroxy-2,2,6,6-tetramethyl-4-propoxypiperidine;

1 -hydroxy-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxapentoxy)piperidine;

4,4′-[1,6-hexanediylbis(formylimino)]bis[2,2,6,6-tetramethyl-1-hydroxypiperdine;

2-(8-carboxyoctyl)-4,4-dimethyl-2-octyl-3-hydroxy-oxazolidine;

3,3-dimethyl-4-hydroxy-1-oxa-4-azaspiro[4.5]decane;

3-aminomethyl-2,2,5,5-tetramethyl-1-hydroxy-pyrrolidine;

3-carboxy-2,2,5,5-tetramethyl-1-hydroxypyrrolidine;

4-phenyl-2,2,5,5-tetramethyl-1-hydroxy-3-imidazoline;

4-phenyl-2,2,5,5-tetramethyl-1-hydroxy-3-imidazoline-3-oxide;

di-tert-butyl hydroxylamine.

The sheets treated with hydroxylamines exhibit substantial inhibition toyellowing compared to the untreated control sheet.

EXAMPLE 3 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, C, D and E.The sheets treated with nitroxides exhibit substantial inhibition toyellowing compared to the untreated control sheet.

Compounds Time in Days Blank B C D E PC Number 0 0 0 0 0 0 0.93 2.490.88 1.6 2.01 1.28 1.9 5.27 1.89 3.24 4.06 2.49 2.94 8.46 3.41 5.52 6.734.28 3.93 10.54 4.36 6.89 8.57 5.4 4.98 12.34 5.36 8.31 10.5 6.53 5.8813.81 6.11 9.45 11.62 7.74 6.91 15.55 7.17 11.05 13.17 8.81 7.98 17.348.18 12.5 14.57 10.12 8.97 19.44 9.33 13.72 16.28 11.32 10.01 20.98 10.115.07 17.75 12.21 10.94 22.35 11.01 16.3 19.1 13.16

EXAMPLE 4 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound EE. The sheetstreated with nitroxides exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

Compound Time in Days EE Blank PC Number 0 0 0 1.04 1.77 4.53 2.02 3.777.91 3.06 5.97 11.16 4.02 7.76 13.72 5.02 9.28 15.47 6.23 10.49 17.616.98 11.88 18.78 7.98 13.06 20.09 10.96 16.92 25.25

EXAMPLE 5 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of each of the followingcompounds:

1-oxyl-2,2,6,6-tetramethyl-1,2,3,6-tetrahydro-pyridine;

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate;

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoate;

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-stearate;

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-benzoate;

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-(4-tert-butyl)benzoate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-succinate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-adipate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-n-butylmalonate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-phthalate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-isophthalate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-terephthalate;

bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-hexahydroterephthalate;

N,N′-bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-adipinamide;

N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-caprolactam;

N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-dodecylsuccinimide;

2,4,6-tris-[N-butyl-N-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl]-s-triazine;

4,4′-ethylenebis(1-oxyl-2,2,6,6-tetramethylpiperazin-3-one;

tris-(2,2,6,6-tetramethyl-1-oxyl-piperidin-4-yl)phosphite;

1-oxyl-2,2,6,6-tetramethyl-4-methoxypiperidine;

1-oxyl-2,2,6,6-tetramethyl-4-ethoxypiperidine;

1-oxyl-2,2,6,6-tetramethyl-4-propoxypiperidine;

1-oxyl-2,2,6,6-tetramethyl-4-carboxypiperidine;

1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxapentoxy)piperidine;

4,4′-[1,6-hexanediylbis(formylimino)]bis[2,2,6,6-tetramethyl-1-piperdinyloxy;

2-(8-carboxyoctyl)-4,4-dimethyl-2-octyl-3-oxazolidinyloxy;

3,3-dimethyl-1-oxa-4-azaspiro[4.5]dec-4-yloxy;

3-aminomethyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxy;

3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy;

4-phenyl-2,2,5,5-tetramethyl-3-imidazolin-1-yloxy;

4-phenyl-2,2,5,5-tetramethyl-3-imidazolin-1-yloxy-3-oxide;

di-tert-butyl nitroxide.

The sheets treated with nitroxides exhibit substantial inhibition toyellowing compared to the untreated control sheet.

EXAMPLE 6 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds A, F,G, H, Iand J. The sheets treated with hydroxylamine salts exhibit substantialinhibition to yellowing compared to the untreated control sheet.

Time in Compounds Days Blank A F G H I J PC Numbers 0 0 0 0 0 0 0 0 0.773.62 0.90 1.26 1.42 1.23 1.02 1.08 1.74 6.27 1.69 2.29 2.60 2.08 1.971.98 2.81 8.82 2.50 3.23 3.54 2.92 2.8 2.84 3.8 10.97 3.25 4.20 5.0 3.853.65 3.66 4.75 12.86 4.08 5.01 5.52 4.60 4.3 4.44 5.81 14.68 4.88 5.956.6 5.5 5.08 5.36 6.79 16.24 5.62 6.81 7.51 6.27 5.85 6.0 7.8 17.36 6.097.40 8.42 6.97 6.36 6.56 8.76 18.44 6.71 8.13 9.24 7.7 7.02 7.13 9.7519.41 7.33 8.76 9.95 8.3 7.62 7.72 10.8 20.35 7.85 9.43 10.68 8.92 8.268.2 11.87 21.13 8.34 9.98 11.36 9.46 8.68 8.6 12.81 21.98 8.77 10.5212.12 9.98 9.10 9.06

EXAMPLE 7 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds K and L. Thesheets treated with hindered amine hydroxylamine Compounds K and Lexhibit substantial inhibition to yellowing compared to the untreatedcontrol sheet.

Compounds Time in Days Blank K L PC Number 0 0 0 0 .81 3.19 1.42 1.591.82 5.85 2.62 3.02 2.8 8.06 3.93 4.41 3.75 10.02 4.79 5.42 4.83 12.085.85 6.61 5.8 13.81 7.35 7.52 6.76 15.49 7.73 8.40 7.77 16.98 8.39 9.28.74 18.54 9.34 10.36 9.76 20.06 10.02 11.18 10.74 21.56 11.06 12.24

EXAMPLE 8 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds M, N and O.The sheets treated with selected acylated hindered amine hydroxylaminederivatives exhibit substantial inhibition to yellowing compared to theuntreated control sheet.

Compounds Time in Days Blank M N O PC Number 0 0 0 0 0 .82 3.87 2.062.02 2.05 2.72 8.9 5.28 4.87 5.13 3.76 10.88 6.53 6.03 6.42 4.76 15.597.72 7.17 7.62 5.76 14.32 8.92 8.28 8.77 6.77 16.36 10.42 9.61 10.247.81 18.47 11.97 10.94 11.7 8.79 20.15 13.14 12.01 12.86 10 21.9 14.3113.08 13.96 10.77 23.5 15.51 14.02 15.16

EXAMPLE 9 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.5% by weight of each of the following:

1-acetyl-4-Hydroxy-2,2,6,6-tetramethyl-piperidine;

1-Acetyl-2,2,6,6-tetramethyl-piperidin-4-one;

bis(1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate.

The sheets treated with acylated hindered amine derivatives exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet.

EXAMPLE 10 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compound P. The sheetstreated with Compound P exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

Compound Time in Days Blank P PC Number 0 0 0 .81 3.19 1.66 1.82 5.852.68 2.8 8.06 3.76 3.75 10.02 4.64 4.83 12.08 5.50 5.8 13.81 6.28 6.7615.49 7.21 7.77 16.98 7.90 8.74 18.54 8.9 9.76 20.06 9.63 10.74 21.5610.47

EXAMPLE 11 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.5%-0.1% by weight of Compound A and 0.5%by weight of Compound Q. The sheets treated with a combination ofhydroxylamine and benzophenone UVA exhibit substantial inhibition toyellowing compared to the treated control sheet.

Time in Concentration of Compound A Days 0.50 0.40 0.30 0.20 0.10 BlankPC Number 0 0 0 0 0 0 0 1 1.05 0.73 0.71 0.93 0.86 5.74 2.1 2.17 1.631.6 2.11 2.02 10.51 2.98 3.05 2.48 2.43 3.12 3.09 13.75 3.98 4.12 3.413.39 4.37 4.2 16.67 4.97 4.95 4.22 4.16 5.39 5.15 18.96 6.05 5.95 5.185.18 6.59 6.36 21.42

EXAMPLE 12 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A and 0.5% byweight of the UVA compounds R and S. The sheets treated with acombination of hydroxylamine and benzotriazole UVA exhibit substantialinhibition to yellowing compared to the untreated control sheet andillustrate the performance enhancement when combinations ofhydroxylamine and UVA are used.

Compound 0.25% A 0.25% A Time in Days 0.25% A 0.5% R 0.5% S Blank PCNumber 0 0 0 0 0 0.77 0.97 0.21 0.21 3.74 1.85 1.86 0.48 0.54 7.25 2.782.85 0.8 0.83 10.43 5.84 6.42 2.23 2.38 19.5 6.93 7.85 2.93 3.05 21.69 88.82 3.32 3.38 23.25

EXAMPLE 13 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the UVA compound S. The sheets treated with acombination of nitroxide and UVA exhibit substantial inhibition toyellowing compared to the untreated control sheet and illustrate theperformance enhancement when combinations of nitroxide and UVA are used.

Time 0.25% B 0.25% T 0.25% U 0.25% V in Days 0.5% S 0.5% S 0.5% S 0.5% S0.5% S Blank PC Number 0 0 0 0 0 0 0 0.9 0.54 1.02 1.01 0.29 3.37 4.241.9 1.12 2.06 2 2.12 6.49 7.81 2.9 1.86 3.19 3.11 4.17 9.38 10.91 3.962.5 4.52 4.29 6.44 12.31 14.04 7.16 5.03 8.63 8.41 12.92 19.98 22.317.89 5.6 9.58 9.44 14.43 21.54 24.13

EXAMPLE 14 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the benzophenone UVA compounds:

(2-hydroxy-4-octyloxy-phenyl)-phenyl-methanone;

(2-hydroxy-4-methoxy-phenyl)-phenyl-methanone;

(4-dodecyloxy-2-hydroxy-phenyl)-phenyl-methanone;

(2-hydroxy-4-methoxy-phenyl)-(2-hydroxy-phenyl)-methanone;

bis-(2-hydroxy-4-methoxy-phenyl)-methanone;

bis-(2,4-dihydroxy-phenyl)-methanone;

[3-(3-benzoyl-2-hydroxy-6-methoxy-benzyl)-2-hydroxy-4-methoxy-phenyl]-phenyl-methanone:

2-hydroxy-4-methoxybenzophenone-5-sulfonic acid;

2,2′-dihydroxy-4,4′-dimethoxybenzophenone-5,5′-disodium sulfonate.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 15 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the benzotriazole UVA compounds:

(a) 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;

(b) 2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole;

(c) 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole;

(d) 2-(2-hydroxy-3,5-di-α-cumylphenyl)-2H-benzotriazole;

(e) 2-(2-hydroxy-3-α-cumyl-5-tert-octylphenyl)-2H-benzotriazole;

(f) 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole;

(g)3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1-methylpropyl)-benzenesulfonicacid monosodium salt;

(h) 3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamic acidand sodium salt;

(i) 12-hydroxy-3,6,9-trioxadodecyl3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;

(j) octyl3-tert-butyl-4-hydroxy-5-(2H-benzotriazol-2-yl)-hydrocinnamate;

(k)4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine (* is mixture of C₁₂₋₁₄oxy isomers);

(l)4,6-bis(2,4-dimethylphenyl)-2-(4-octyloxy-2-hydroxyphenyl)-s-triazine;

(m) 2,4-dihydroxybenzophenone;

(n) 2,2′,4,4′-tetrahydroxy-5,5′-disulfobenzophenone, disodium salt;

(o) 2-hydroxy-4-octyloxybenzophenone;

(p) 2-hydroxy-4-dodecyloxybenzophenone;

(q) 2,4-dihydroxybenzophenone;

(r) 2,2′,4,4′-tetrahydroxybenzophenone;

(s) 4-aminobenzoic acid;

(t) 2,3-dihydroxypropyl-4-aminobenzoic acid;

(u) 3-(4-imidazolyl)acrylic acid;

(v) 2-phenyl-5-benzimidazole sulfonic acid;

(w) N,N,N-trimethyl-α-(2-oxo-3-bornylidene)-p-toluidinium methylsulfate;

(x) 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, sodium salt;

(y)3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxy-N,N,N-trimethyl-1-propanaminiumchloride;

(z)3-[4-(2H-benzotriazol-2-yl)-3-hydroxyphenoxy]-2-hydroxy-N,N,N-trimethyl-1-propanaminium,chloride;

(aa) 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 16 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the triazine UVA compounds:

4,6-bis(2,4-dimethylphenyl)-2-(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine(* mixture of C₁₂₋₁₄oxy isomers) (Tinuvin 400);

4,6-bis(2,4-dimethylphenyl)-2-(2-hydroxy-4-octyloxyphenyl)-s-triazine;

2,4,6-tris(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-s-triazine(* mixture of C₁₂₋₁₄oxy isomers);

2,4-bis(4-(3-dodecyloxy*-2-hydroxypropoxy)-2-hydroxyphenyl)-6-(2,4-dimethylphenyl)-s-triazine(* mixture of C₁₂₋₁₄oxy isomers).

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 17 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the cinnamate UVA compounds:

2-cyano-3,3-diphenyl-2-propenoic acid ethyl ester;

2-cyano-3,3-diphenyl-2-propenoic acid 2-ethylhexyl ester;

3-(4-methoxyphenyl)-2-propenoic acid 2-ethylhexyl ester.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 18 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the oxalanilide UVA compounds:

N-(2-ethoxyphenyl)-N′-(4-isododecylphenyl)-ethanediamide;

N-(2-ethoxyphenyl)-N′-(2-ethylphenyl)-ethanediamide.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 19 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the salicylate UVA compounds:

2-hydroxy-benzoic acid phenyl ester;

2-hydroxy-benzoic acid 4-(1,1-dimethylethyl)phenyl ester;

2-hydroxy-benzoic acid 2-ethylhexyl ester;

2-hydroxy-benzoic acid 4-isopropylbenzyl ester;

2-hydroxy-benzoic acid 3,3,5-trimethylcyclohexyl ester.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 20 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the formamidine UVA compounds:

4-[[(methylphenylamino)methylene]amino]-benzoic acid, ethyl ester;

4-[[(ethylphenylamino)methylene]amino]-benzoic acid, ethyl ester.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 21 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the 4-hydroxybenzoate UVA compounds:

3,5-bis(1,1-dimethylethyl)-4-hydroxy-benzoic acid hexadecyl ester;

3,5-bis(1,1-dimethylethyl)-4-hydroxy-benzoic acid2,4-bis(1,1-dimethylethyl)phenyl ester.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 22 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compounds B, T, U and Vand 0.5% by weight of the 4-aminobenzoate UVA compounds:

4-aminobenzoic acid;

2,3-dihydroxypropyl-4-aminobenzoate;

2-ethylhexyl 4-dimethylaminobenzoate;

ethyl 4-[bis(2-hydroxypropyl)amino]benzoate.

The sheets treated with a combination of nitroxide and UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet and illustrate the performance enhancement when combinations ofnitroxide and UVA are used.

EXAMPLE 23 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds A, F, G, H, Iand J and 0.5% of Compound R. The sheets treated with hydroxylaminesalts and UVA exhibit substantial inhibition to yellowing compared tothe untreated control sheet.

Time in 0.5% G 0.5% H 0.5% F 0.5% I 0.5% J 0.5% A Days 0.5% R 0.5% R0.5% R 0.5% R 0.5% R 0.5% R Blank PC Number 0 0 0 0 0 0 0 0 0.76 0.57−0.14 0.06 0.16 −0.18 −0.55 3.51 1.85 0.96 0.02 0.32 0.33 0 −0.49 6.432.81 1.55 0.17 0.63 0.57 0.25 −0.33 8.77 3.76 1.94 0.38 0.9 0.81 0.48−0.21 10.89 4.82 2.52 0.57 1.24 1.01 0.66 −0.06 12.99 5.8 2.89 0.68 1.491.17 0.87 0.05 14.7 6.82 3.27 0.81 1.64 1.38 1.06 0.14 16.03 7.77 3.841.05 2 1.59 1.29 0.3 17.33 8.76 4.05 1.16 2.17 1.75 1.42 0.43 18.22 9.814.77 1.38 2.46 1.98 1.67 0.57 19.27 10.88 5.11 1.53 2.69 2.27 1.86 0.6920.18 11.82 5.51 1.7 2.97 2.45 2.08 0.84 21.03 12.78 5.77 1.89 3.13 2.72.25 0.92 22.03

EXAMPLE 24 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds K and L and0.5% by weight of Compound S. The sheets treated with hindered aminehydroxylamine Michael adduct derivatives and a UVA exhibit substantialinhibition to yellowing compared to the untreated control sheet.

0.5% K 0.5% L Time in Days 0.5% S 0.5% S 0.5% S Blank PC Number 0 0 0 00 0.81 0 0.04 0.29 3.03 1.82 0.51 0.87 0.89 5.78 28 1.08 1.1 1.47 8.113.75 1.56 1.65 2.14 10.21 4.83 2.04 2.25 2.83 12.33 5.8 2.64 2.76 3.5614.13 6.76 2.98 3.23 4.18 15.6 7.77 3.54 3.82 4.93 17.45 8.74 3.97 4.455.7 18.98 9.75 4.6 5.18 6.5 30.34 10.74 5.07 5.85 7.39 21.91

EXAMPLE 25 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compounds M, N and O and0.5% by weight of the UVA Compound W. The sheets treated with selectedacylated hindered amine hydroxylamine derivatives and the UVA exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet.

Time in 0.5% M 0.5% N 0.5% O Days 0.5% W 0.5% W 0.5% W 0.5% W Blank PCNumber 0 0 0 0 0 0 .82 0.59 0.46 0.51 .79 3.87 2.72 1.84 1.46 1.77 2.258.9 3.76 2.43 1.91 2.46 2.90 10.88 4.76 3.09 2.34 3.12 3.52 12.59 5.763.84 2.9 3.87 4.32 14.32 6.77 4.75 3.59 4.72 5.12 16.36 7.81 5.7 4.375.68 6.09 18.47 8.79 6.55 4.98 6.46 6.86 20.15 10.0 7.43 5.45 7.37 7.721.9 10.77 8.28 6.19 8.28 8.64 23.5

EXAMPLE 26 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.50% by weight of Compound P and 0.5%Compound S. The sheets treated with selected NOR derivative incombination with a UVA exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

0.5% P Time in Days 0.5% S 0.5% S Blank PC Number 0 0 0 0 0.81 0.06 0.293.03 1.82 0.46 0.89 5.78 2.8 0.95 1.47 8.11 3.75 1.37 2.14 10.21 4.831.74 2.83 12.33 5.8 2.13 3.56 14.13 6.76 2.5 4.18 15.6 7.77 2.95 4.9317.45 8.74 3.42 5.7 18.98

EXAMPLE 27 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with and 0.5% Compound S and 0.5% by weight of:

1-acetyl-4-Hydroxy-2,2,6,6-tetramethyl-piperidine;

1-Acetyl-2,2,6,6-tetramethyl-piperidin-4-one;

bis(1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate.

The sheets treated with acylated hindered amine derivatives incombination with a UVA exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

EXAMPLE 28 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A, 0.5%compound W and 0.5% of Compound X. The sheets treated withhydroxylamine, UVA and PEO exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

0.25% A 0.25% A 0.5% W Time in Days 0.25% A 0.5% W 0.5% X Blank PCNumber 0 0 0 0 0 0.77 0.97 0.06 0.03 3.74 1.85 1.86 0.28 0.27 7.25 2.782.85 0.49 0.46 10.43 5.84 6.42 1.54 1.48 19.5 6.93 7.85 2 1.98 21.69 88.82 2.34 2.26 23.25

EXAMPLE 29 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A, 0.5%Compound Y, Z and AA and 0.5% of Compound X. The sheets treated withhydroxylamine, UVA and PEO exhibit substantial inhibition to yellowingcompared to the untreated control sheet.

Time in 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% Blank Days A A A A AA * A 0.5% Y 0.5% Y 0.5% Z 0.5% Z 0.5% A 0.5% A 0.5% X 0.5% X A A 0.5% XPC Number 0 0 0 0 0 0 0 0 0 0.84 1.22 0.34 0.27 1.11 1.09 0.33 0.22 41.77 1.94 0.64 0.45 1.32 1.54 0.53 0.43 7.73 4.88 5.48 2.41 1.86 3.874.9 2.39 1.67 18.19 5.92 6.9 3.11 2.46 4.82 5.82 3.01 2.09 21.03 6.997.64 3.64 2.81 5.34 6.51 3.48 2.41 22.93

EXAMPLE 30 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.5% by weight of Compound G, 0.25% byweight of Compound W and 0.25% by weight of Compound BB. The sheetstreated with hydroxylamine, UVA and metal chelating agent exhibitsubstantial inhibition to yellowing compared to the untreated controlsheet.

Time in 0.5% G 0.5% G 0.5% G 0.5% G 0.25% BB Blank Days 0.25% W 0.25% BB0.25% W 0.25% BB PC Number 0 0 0 0 0 0 0 0.83 0.13 0.69 0.23 0.76 3.63.68 1.79 0.37 1.26 0.48 1.33 6.17 6.19 2.77 0.58 1.82 0.72 1.87 8.418.45 3.81 0.84 2.44 1.01 2.46 10.48 10.49 4.9 1.14 3.02 1.35 2.99 12.3612.19 5.83 1.37 3.53 1.62 3.51 14.05 13.82 6.8 1.62 4.1 1.87 4.07 15.8215.39 7.77 1.93 4.67 2.23 4.69 17.31 16.59

EXAMPLE 31 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound B, 0.5% byweight of Compound Q and 1.0% by weight of Compound CC or DD. Theresults show the effectiveness of nitrones alone, nitrones with a UVA,nitrones with a nitroxide and especially nitrone with a UVA and anitroxide in inhibition to yellowing compared to the untreated controlsheet.

Time in 0.5% Q 0.5% Q 0.5% Q 0.5% Q 0.5% Q 0.25% 0.25% 1% CC 1% DD BlankDays 0.25% B 025% 1% CC 1% DD B B 1% CC B 1% CC 1% DD 1% DD PC Number 00 0 0 0 0 0 0 0 0 0 0.74 −1.25 0.13 −0.43 0.25 0.55 −0.43 0.85 0.28 2.143.22 1.74 −0.92 0.45 −0.16 0.72 1.19 0.28 2.49 1.82 4.78 7.24 2.82 −0.590.84 0.25 1.26 1.82 0.83 3.83 3.69 6.68 9.77 3.83 −0.41 1.33 0.93 1.882.63 1.63 5.09 5.88 8.34 12.42 4.76 −0.19 1.75 1.7 2.56 3.53 2.53 6.137.8 9.8 14.78 5.75 −0.01 2.08 2.54 3.13 4.41 3.3 6.87 9.63 11.14 16.896.77 0.19 2.51 3.35 3.77 5.36 3.96 7.67 11.25 12.33 19.13 7.75 0.44 2.914.14 4.36 6.13 4.56 8.23 12.39 13.16 20.09 8.77 0.63 3.22 5.07 4.87 6.945.27 8.84 13.87 14 21.84

EXAMPLE 32 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.5% by weight of Compound Q and 0.25% byweight of Compounds D, B, C, E and A. The results show the superiorityof hydroxylamines over nitroxides in maintaining a high brightness ofthe paper upon application and during exposure.

Time in 0.5% Q 0.5% Q 0.5% Q 0.5% Q 0.5% Q 0.5% Q Blank Days 0.25% D0.25% B 0.25% C 0.25% E 0.25% A ISO Brightness 0 78.83 76.96 76.75 78.2479.85 79.75 78.6 0.75 77.45 77.53 77.15 76.21 78.91 75.36 68.43 1.7475.77 77.16 76.66 74.36 78.48 72.22 62.89 2.74 73.61 76.59 75.89 72.177.7 68.93 58.54 3.75 71.95 75.96 75.21 70.14 77.12 66.09 55.41 6.8165.96 72.86 72.02 64.11 74.09 58.58 49.29

EXAMPLE 33 Accelerated Yellowing with High Intensity Lamps

Additives are added with a sizing treatment on 100% BTMP paper coatedwith 2 g/m²/side using a Pilot Liquid Application System from BonnierTechnology Group Inc. (LAS System). It consists of a hydrophilic roll,soft metering roll, soft backing roll, and sizing pan. A film of sizingsolution is drawn through the metering nip onto the hydrophilic roll.The paper gets sized when it runs between the hydrophilic roll and thebacking roll.

Commercial name Chemical Nature Parts Penford ® Gum 280 Hydroxyethylatedstarch 80 Acronal ® S728 N-Butylacrylate & styrene copolymer 20dispersion Total solids content of 20%, pH around 7.0

Sizing Sizing 0.36% G 0.24% G Time in Days Blank Sizing only 0.84% S0.55% S PC Number 0 0 0 0 0 1.01 4.69 4.45 0.59 0.95 1.85 6.78 6.51 0.791.53 2.9 8.95 8.98 1.04 1.91 4.1 11.61 10.68 1.41 2.51 4.8 13.29 12.121.66 2.84 5.81 14.75 13.98 1.89 3.23 6.77 16.15 15.26 2.04 3.66 7.8217.16 16.27 2.42 3.85 8.78 18.17 17.19 2.45 4.22 9.89 19.28 18.19 2.664.42 10.92 21.11 19.45 3.02 4.97 11.81 20.8 20.31 3.18 5.37 12.81 21.9821.18 3.55 5.58 13.79 22.68 22.16 3.65 5.99

EXAMPLE 34 Accelerated Yellowing with High Intensity Lamps

Additives are added with a pigmented sizing treatment on 100% BTMP papercoated with 2 g/m²/side using a Pilot Liquid Application System fromBonnier Technology Group Inc. (LAS System). It consists of a hydrophilicroll, soft metering roll, soft backing roll, and sizing pan. A film ofsizing solution is drawn through the metering nip onto the hydrophilicroll. The paper gets sized when it runs between the hydrophilic roll andthe backing roll.

100% BTMP paper coated with 4 g/m²/side pigments based coatingformulation:

Commercial name Chemical Nature Parts Covercarb ® Ultrafine groundcalcium carbonate 80 Astraplate ® Delaminated clay 20 Penford ® Gum 280Hydroxyethylated starch 6 Acronal ® S728 N-Butylacrylate & styrenecopolymer 12 dispersion Sterocoll ® AL Anionic water-in-oil emulsion ofan 0.1 acrylamide-acrylic copolymer AZCOTE ® 5800M Ammonium zirconiumcarbonate solution 0.5 Total solids content of 57%, pH around 8.0

Coating Coating Coating Time in 0.13% G 0.4% G 0.19% G Days BlankCoating only 0.4% S 0.74% S 0.48% S PC Number 0 0 0 0 0 0 1 4.46 3.660.65 0.16 0.7 1.83 7.16 5.15 1.03 0.31 1.15 2.91 8.54 6.7 1.21 0.43 1.414.11 11.04 8.47 1.53 0.59 1.61 4.8 13.08 10.55 2.1 0.59 1.96 5.82 14.2511.19 2.02 0.8 2.16 6.78 16.01 12.44 2.39 0.92 2.54 7.83 17.45 13.672.61 1.02 2.7 8.8 18.09 14.08 2.68 0.98 2.86 9.9 18.9 14.88 2.95 1.093.02 10.94 20.19 15.67 3.12 1.21 3.28 11.81 21.38 16.68 3.59 1.31 3.5712.82 22.25 17.57 3.58 1.46 3.75 13.8 23.26 18.21 3.83 1.59 4.27

EXAMPLE 35

Using the accelerated test method, BTMP handsheets containing variouscombinations of 0.25% by weight of a hindered amine, 0.5% by weight ofan s-triazine UV absorber and/or 0.5% by weight of a polymeric additivesare compared for efficacy in preventing yellowing. The data arepresented on the table below.

Table for Example 35 Square Names A B C D E F G H I J K Days PC Numbers1.14 2.56 1.937 2.557 .1627 .2688 .6753 2.754 1.833 2.188 1.927 5.3191.97 4.40 3.214 4.042 .4481 .5323 1.249 4.484 2.987 3.643 3.219 8.0642.98 6.20 4.546 5.752 .7997 .9261 1.873 6.326 4.360 5.338 4.778 10.994.06 9.04 6.210 7.590 1.287 1.460 2.742 8.403 5.855 6.964 6.352 13.955.03 11.50 8.252 9.841 2.087 2.228 3.957 10.64 7.498 9.008 8.229 17.205.98 12.74 9.404 11.19 2.466 2.582 4.593 12.16 8.572 10.13 9.295 19.286.96 14.25 10.54 12.58 2.747 2.889 5.203 13.25 9.360 11.04 10.18 21.017.98 16.48 12.23 14.65 3.541 3.792 6.425 15.24 11.07 12.66 11.74 23.52 Acontains the UV absorber TINUVIN ® 400; Compound Y. B contains the UVabsorber TINUVIN ® 400 and the polymer PEO. C contains the UV absorberTINUVIN ® 400 and the polymer PTHF. D contains the hindered aminenitroxide Compound B, the UV absorber TINUVIN ® 400 and the polymer PEO.E contains the hindered amine nitroxide Compound B, the UV absorberTINUVIN ® 400 and the polymer PTHF. F contains the hindered aminenitroxide Compound B and the UV absorber TINUVIN ® 400. G contains thehindered amine nitroxide Compound JJ and the UV absorber TINUVIN ® 400.H contains the hindered amine nitroxide Compound B. I contains thehindered amine TEMPO. J contains the hindered amine TEMPO. K is thecontrol containing no stabilizer additives.

As inspection of the data on the table attests, in best to poorest orderD≅E>F>H>J>B>I>C>G>A>>K. These data show that the combination of anitroxide, a UV absorber and a polymer coadditive provides the bestprotection against yellowing after 8 days exposure.

EXAMPLE 36

Using the accelerated test method, BTMP handsheets containing variouscombinations of 0.25% by weight of a hindered amine, 0.5% by weight of abenzophenone UV absorber and/or 0.5% by weight of a polymeric additivesare compared for efficacy in preventing yellowing. The data arepresented on the table below.

Table for Example 36 Square Names A B C D E F G H I Days PC Numbers .8221.89 1.545 1.784 .0633 .0881 .0211 1.574 .9791 3.826 1.87 3.41 2.7333.241 .3018 .2650 .1786 2.911 2.048 6.978 2.91 5.00 4.254 4.939 .6705.5656 .4648 4.489 3.249 10.19 3.87 6.96 6.038 6.875 1.371 1.183 1.1006.319 4.770 13.68 4.83 8.59 7.534 8.702 1.808 1.484 1.334 7.759 5.90316.43 5.81 9.93 8.690 9.944 2.031 1.658 1.483 8.810 6.785 18.26 6.8311.80 10.37 11.67 2.704 2.217 2.079 10.34 7.968 21.39 7.82 13.59 11.9913.49 3.288 2.653 2.559 11.53 9.169 23.91 A contains the UV absorberUVINUL ® 3000. B contains the UV absorber UVINUL ® 3000 and the polymerPEO. C contains the UV absorber UVINUL ® 3000 and the polymer PTHF. Dcontains the hindered amine nitroxide Compound B, the UV absorberUVINUL ® 3000 and the polymer PEO. E contains the hindered aminenitroxide Compound B, the UV absorber UVINUL ® 3000 and the polymerPTHF. F contains the hindered amine nitroxide Compound B and the UVabsorber UVINUL ® 3000. G contains the hindered amine Compound JJ andthe UV absorber UVINUL ® 3000. H contains the hindered amine nitroxideCompound B. I is the control containing no stabilizer additives.

As inspection of the data on the table attests, in best to poorest orderF>E>D>H>G>B>C≅A>>I. These data show that the combination of a nitroxideand a benzophenone UV absorber coadditive provides the best protectionagainst yellowing after 8 days exposure.

EXAMPLE 37

Using the accelerated test method, BTMP handsheets containing variouscombinations of 0.25% by weight of a hindered amine, 0.5% by weight of abenzophenone UV absorber and/or 0.5% by weight of a polymeric additivesare compared for efficacy in preventing yellowing. The data arepresented on the table below.

Table for Example 37 Square Names A B C D E F G Days PC Numbers 1.013.60 3.621 1.383 1.764 3.454 1.221 5.048 2.09 6.42 6.027 2.412 3.2005.842 2.501 8.506 3.05 9.03 8.646 3.845 5.012 8.433 4.123 12.04 4.0111.60 11.21 4.957 6.360 10.54 5.245 15.26 4.98 13.19 13.01 4.412 7.39611.92 6.115 17.50 6.01 15.49 15.26 6.252 9.151 14.34 7.611 20.59 7.0017.75 17.67 7.653 10.83 16.64 8.926 23.32 A contains the UV absorberUVINUL ® 3048; Compound Z. B contains the UV absorber UVINUL ® 3048 andthe polymer PEO. C contains the hindered amine nitroxide Compound F, theUV absorber UVINUL ® 3048 and the polymer PEO. D contains the hinderedamine nitroxide Compound B and the UV absorber UVINUL ® 3048. E containsthe hindered amine Compound JJ and the UV absorber UVINUL ® 3048. Fcontains the hindered amine nitroxide Compound B. G is the controlcontaining no stabilizer additives.

As inspection of the data on the table attests, in best to poorest orderC>F>D>E>B≅A>>G. These data show that the combination of a nitroxide, abenzophenone UV absorber and polymer coadditive provides the bestprotection against yellowing after 7 days exposure.

The tables in Examples 38 to 48 all show PC Numbers.

EXAMPLE 38

Using the accelerated test method, BTMP handsheets containing variouscombinations of 1% by weight of a hindered amine, 0.5% by weight of abenzotriazole UV absorber and/or 0.5% by weight of a polymeric additivesare compared for efficacy in preventing yellowing. The data arepresented on the table below.

Table for Example 38 Days A B C D E F G H 0 0 0 0 0 0 0 0 0 1.17 1.620.91 1.13 1.4 2.26 2.85 3.35 3.42 2 3 1.81 2.18 2.24 3.69 4.42 5.07 5.262.98 4.23 2.62 3.15 3.14 5.21 5.9 6.75 7.22 4 5.67 3.58 4.32 4.44 7.267.81 9.09 9.87 5.01 6.73 4.28 5.2 5.13 8.84 9.08 10.48 11.72 5.99 7.735.01 5.98 6.08 10.64 10.49 12.11 13.69 6.94 8.75 5.74 6.79 6.75 11.9111.42 13.29 14.95 7.98 9.62 6.46 7.55 7.48 13.25 12.44 14.36 16.48 8.9910.27 6.99 8.14 8.2 14.63 13.54 15.66 18.25 9.98 10.6 7.36 8.56 9.0316.1 14.56 16.81 19.97 11.01 11.34 7.96 9.27 9.93 17.85 15.9 18.37 21.8412.01 13.48 9.17 10.27 10.57 19.04 16.65 19.19 23.03 A contains thehindered amine TMHP, the UV absorber TINUVIN ® 1130 and the polymer PEO.B contains the hindered amine TMHP, the UV absorber TINUVIN ® 1130 andthe polymer PTHF. C contains the hindered amine TMHP and the UV absorberTINUVIN ® 1130. D contains the hindered amine Compound G and the UVabsorber TINUVIN ® 1130. E contains the UV absorber TINUVIN ® 1130. Fcontains the hindered amine TMHP. G contains the hindered amine CompoundJJ. H is the control containing no stabilizer additives.

As inspection of the data on the table attests, in best to poorest orderD>B>C>F>A>E>G>H. These data show that the combination of a hinderedamine and a benzotriazole UV absorber coadditive provides the bestprotection against yellowing after 12 days exposure.

EXAMPLE 39

Using the ambient test method, BTMP handsheets containing 1%, 0.6% or0.1% by weight of the hindered amine nitroxide Compound F, 2% by weightof the benzotriazole UV absorber TINUVIN® 328 and 1% by weight of thepolymer PEO are compared for efficacy in preventing yellowing. The dataare presented on the table below.

Table for Example 39 Days p51a p51b p51c p51d p51e 0 0.00 0.00 0.00 0.00.0.00 1 0.10 −0.08 −0.37 −0.24 −0.21 5 0.54 −0.18 −0.84 −0.64 −0.54 71.07 −0.04 −0.67 −0.47 −0.30 8 1.00 −0.12 −0.83 −0.63 −0.42 9 1.37 −0.04−0.73 −0.50 −0.32 11 1.70 −0.10 −0.97 −0.67 −0.44 13 2.05 −0.08 −0.93−0.61 −0.40 15 2.33 −0.13 −1.09 −0.73 −0.46 29 4.29 −0.02 −1.12 −0.67−0.20 40 5.86 0.00 −1.16 −0.69 −0.13 55 7.52 0.03 −1.12 −0.60 0.18 597.88 0.02 −1.16 −0.60 0.22 66 8.83 0.05 −1.12 −0.55 0.39 69 9.05 0.01−1.21 −0.67 0.35 73 9.56 0.09 −1.10 −0.53 0.49 80 10.48 0.14 −1.01 −0.440.64 87 10.91 0.10 −1.12 −0.56 0.55 94 12.11 0.28 −0.91 −0.37 0.83 11113.38 0.32 −0.86 −0.29 1.01 122 14.71 0.52 −0.67 −0.10 1.32 129 14.600.37 −0.79 −0.19 1.38 136 15.92 0.50 −0.60 0.17 1.77 143 16.20 0.58−0.47 0.28 1.99 150 16.68 0.52 −0.52 0.26 2.06 157 17.40 0.61 −0.40 0.342.16 164 18.08 0.67 −0.31 0.40 2.41 171 19.54 0.75 −0.13 0.58 2.82 17819.98 0.89 −0.09 0.63 3.01 185 20.39 0.90 −0.07 0.69 3.23 188 20.70 0.83−0.02 0.70 3.39 191 21.64 0.92 −0.12 0.66 3.41 199 22.11 0.85 −0.10 0.703.52 206 22.94 0.97 −0.02 0.75 3.71 213 23.59 0.91 0.03 0.82 3.82 22024.34 0.95 −0.02 0.81 3.90 A is the control containing no stabilizeradditives. B is a control which is a Kraft handsheet. C contains 1% ofthe nitroxide. D contains 0.6% of the nitroxide. E contains 0.1% of thenitroxide.

As inspection of the data on the table attests, in best to poorest orderC≅D≅B>E>>>A. These data show that the nitroxide provides resistance toyellowing particularly at the 0.6 and 1% by weight levels that makes thecolor after 220 days of exposure essentially equal to that obtained withKraft paper. Even at the 0.1% level, the nitroxide provides very goodresistance to yellowing.

EXAMPLE 40

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25%, 0.2%, 0.15%, 0.1% or 0.05% byweight of the hindered amine nitroxide Compound F are compared forefficacy in preventing yellowing. The data are presented on the threetables below respectively.

Accelerated Test Method Time a b c d e f 0.00 0.00 0.00 0.00 0.00 0.000.00 24.33 2.27 2.55 3.16 3.46 3.68 5.18 48.50 4.17 4.52 5.46 6.05 6.298.60 73.25 5.71 6.18 7.46 8.05 8.62 11.65 97.00 7.42 7.94 9.39 10.3410.97 14.68 121.50 9.00 9.57 11.42 12.57 13.17 17.34 144.50 10.56 11.2813.32 14.53 15.36 20.05 168.25 12.04 12.84 15.08 16.52 17.39 22.57

Time a b c d e f Ambient Test Method 0.00 0.00 0.00 0.00 0.00 0.00 0.003.02 0.39 0.21 0.39 0.49 0.44 0.80 10.01 1.00 0.63 1.01 1.23 1.27 2.0417.00 1.33 0.90 1.44 1.78 1.82 3.01 31.03 1.97 1.44 2.43 2.88 3.09 5.0438.06 2.71 1.98 3.18 3.73 4.04 6.34 4.5.15 3.24 2.50 3.84 4.48 4.80 7.3352.15 3.59 2.77 4.22 4.94 5.37 8.00 55.02 3.60 2.72 4.22 4.99 5.49 8.2162.02 4.31 3.28 5.04 5.91 6.36 9.28 66.00 4.49 3.38 5.27 6.03 6.63 9.78Dark Aging Test Method 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.06 0.18 0.120.16 0.19 0.17 0.18 10.04 0.23 0.18 0.21 0.23 0.22 21.02 0.16 0.13 0.160.19 0.19 0.31 24.17 0.23 0.18 0.21 0.26 0.25 0.41 38.16 0.16 0.12 0.150.21 0.23 0.48 45.15 0.21 0.17 0.21 0.27 0.28 0.57 52.01 0.20 0.15 0.190.25 0.26 0.58 62.96 0.20 0.15 0.21 0.27 0.28 0.67 A contains 0.25% ofthe nitroxide. B contains 0.2% of the nitroxide. C contains 0.15% of thenitroxide. D contains 0.1% of the nitroxide. E contains 0.05% of thenitroxide. F is a control containing no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order A>B>C>D>E>F. These data show that the nitroxideprovides resistance to yellowing after 168 hours of acceleratedphotoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order B>A>C>D>E>>F. These data show that the nitroxideprovides resistance to yellowing after 66 days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order B>C>A>D>E>>F. These data show that the nitroxide providesresistance to yellowing after 63 days of dark aging.

EXAMPLE 41

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25% by weight of the hindered aminenitroxide Compound F and 1%, 0.5%, 0.25%, 0.2% or 0.1% by weight of thebenzotriazole UV absorber TINUVIN® 1130 are compared for efficacy inpreventing yellowing. The data are presented on the three tables belowrespectively.

Time a b c d e f 0.00 0.00 0.00 0.00 0.00 0.00 0.00 24.50 0.28 0.53 1.141.30 1.88 5.39 49.25 0.57 0.93 1.96 2.35 3.38 8.92 72.55 0.86 1.46 2.843.44 4.83 12.23 97.50 1.20 1.92 3.66 4.57 6.35 15.14 120.50 1.66 2.544.72 5.87 7.97 18.18 144.25 2.02 3.06 5.56 6.98 9.39 20.82 168.50 2.573.73 6.71 8.34 11.05 23.47 Ambient Test Method 0.00 0.00 0.00 0.00 0.000.00 0.00 2.02 0.09 −0.03 0.03 −0.02 0.00 0.41 9.01 0.42 0.26 0.42 0.360.49 1.75 16.00 0.48 0.22 0.45 0.51 0.72 2.75 23.02 0.58 0.38 0.73 0.791.05 3.90 30.05 0.64 0.43 0.95 0.99 1.31 4.79 37.07 0.94 0.71 1.34 1.411.84 6.17 44.15 1.11 0.96 1.72 1.76 2.27 7.26 51.15 1.20 1.04 1.87 1.942.55 7.98 54.03 1.31 1.09 1.95 1.96 2.54 8.27 61.02 1.49 1.29 2.35 2.353.04 9.29 64.98 1.44 1.33 2.43 2.38 3.14 9.73 Dark Aging Test Method 0.00 0.00 0.00 0.00 0.00 0.00 0.00  2.06 0.05 0.02 −0.01 −0.01 0.000.02  9.04 0.12 0.10 0.05 0.06 0.08 0.15 20.02 0.05 0.01 −0.03 −0.030.00 0.13 23.17 0.15 0.07 0.03 0.06 0.05 0.21 30.17 0.06 0.00 −0.04−0.05 −0.03 0.20 37.17 0.10 0.00 −0.02 −0.04 0.00 0.26 44.15 0.13 0.080.00 0.03 0.06 0.33 51.06 0.15 0.03 −0.01 0.00 0.04 0.37 61.96 0.14 0.01−0.01 −0.01 0.05 0.43 79.06 0.30 0.07 0.08 0.01 0.13 0.51 A contains 1%of the UV absorber. B contains 0.5% of the UV absorber. C contains 0.25%of the UV absorber. D contains 0.2% of the UV absorber. E contains 0.1%of the UV absorver. F is a control containing no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order A>B>C>D>E>>F. These data show that thenitroxide plus UV absorber provides resistance to yellowing after 168hours of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order B>A>C>D>E>>F. These data show that the nitroxideplus UV absorber provides resistance to yellowing after 65 days ofambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order D>B>C>E>A>F. These data show that the nitroxide plus UVabsorber provides resistance to yellowing after 79 days of dark aging,but that in the dark the UV absorber is much less critical for efficacy.

EXAMPLE 42

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25% by weight of the hindered aminenitroxide Compound B and 1%, 0.75%, 0.5%, 0.25% or 0.1% by weight of thepolymer PTHF are compared for efficacy in preventing yellowing. The dataare presented on the three tables below respectively.

Time a b c d e f Accelerated Test Method 0.00 0.00 0.00 0.00 0.00 0.000.00 25.00 1.42 1.08 1.50 1.58 1.57 4.56 48.75 2.41 1.98 2.64 2.82 2.867.58 73.25 3.63 3.07 4.04 4.37 4.46 11.08 96.25 4.88 4.12 5.38 5.78 5.9514.07 120.00 5.90 5.14 6.62 7.20 7.41 16.88 144.25 7.20 6.22 8.14 8.648.84 19.74 Ambient Test Method 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8.000.37 0.24 0.17 0.41 0.45 1.66 14.99 0.39 0.32 0.38 0.56 0.73 2.74 22.010.59 0.55 0.66 0.96 1.10 3.90 29.02 0.78 0.74 0.85 1.25 1.42 4.88 36.071.21 1.13 1.24 1.50 2.06 6.21 50.14 1.59 1.44 1.66 2.33 2.57 7.93 53.011.66 1.51 1.73 2.37 2.65 8.16 60.01 2.06 1.76 2.13 2.90 3.16 9.22 63.972.03 1.81 2.16 3.05 3.36 9.73 70.99 2.29 2.07 2.60 3.55 3.89 10.75 77.972.55 2.27 2.81 3.85 4.31 11.64 Dark Aging Test Method 0.00 0.00 0.000.00 0.00 0.00 0.00 1.05 −0.12 −0.13 −0.10 −0.09 −0.08 −0.06 8.03 −0.12−0.10 −0.07 −0.09 −0.08 0.05 19.01 −0.19 −0.18 −0.15 −0.18 −0.17 0.0222.16 −0.13 −0.12 −0.10 −0.10 −0.10 0.10 29.16 −0.23 −0.21 −0.22 −0.19−0.21 0.08 36.16 −0.21 −0.17 −0.16 −0.17 −0.19 0.17 50.05 −0.21 −0.16−0.15 −0.17 −0.19 0.28 A contains 1% of the polymer PTHF. B contains0.75% of the polymer PTHF. C contains 0.5% of the polymer PTHF. Dcontains 0.25% of the polymer PTHF. E contains 0.1% of the polymer PTHF.F is a control containing no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order B>A>C>D>E>>F. These data show that thenitroxide plus polymer provides resistance to yellowing after 144 hoursof accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order B>A>C>D>E>>F. These data show that the nitroxideplus polymer provides resistance to yellowing after 78 days of ambientphotoaging.

During dark aging, inspection of the data on the table shows in best topoorest order A>E>D>B>C>>>F. These data show that the nitroxide pluspolymer provides resistance to yellowing after 50 days of dark aging.

EXAMPLE 43

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25% by weight of the hindered aminenitroxide Compound B, 1%, 0.5%, 0.25%, 0.2% or 0.1% by weight of thebenzotriazole UV absorber TINUVIN® 1130 and 0.5% by weight of polymerPTHF are compared for efficacy in preventing yellowing. The data arepresented on the three tables below respectively.

Time a b c d e f Accelerated Test Method 0.00 0.00 0.00 0.00 0.00 0.000.00 23.42 −0.01 0.48 0.60 0.47 1.34 4.52 47.25 0.34 1.22 1.32 1.18 2.658.11 71.75 0.71 1.91 2.00 1.80 3.81 11.04 96.17 1.04 2.62 2.72 2.49 4.9013.60 119.75 1.64 3.42 3.51 3.28 6.40 16.52 145.75 2.30 5.05 5.11 4.658.26 20.82 168.08 2.73 5.60 5.59 5.22 9.24 22.57 Ambient Test Method0.00 0.00 0.00 0.00 0.00 0.00 0.00 6.98 −0.14 0.20 −0.01 0.07 0.48 1.7913.97 −0.11 0.35 0.04 0.21 0.48 2.63 20.99 −0.04 0.58 0.25 0.44 0.743.73 28.01 0.02 0.71 0.37 0.63 1.01 4.73 35.04 0.24 1.06 0.64 0.98 1.416.01 42.11 0.47 1.28 0.91 1.26 1.79 7.02 49.11 0.55 1.29 0.88 1.36 1.877.78 51.99 0.61 1.33 0.95 1.45 1.91 8.07 59.11 0.79 1.70 1.24 1.72 2.409.32 62.97 0.76 1.78 1.25 1.77 2.52 9.70 69.97 1.16 2.09 1.59 2.14 3.0010.88 77.01 1.25 2.27 1.64 2.30 3.27 11.75 Dark Aging Test Method 0.000.00 0.00 0.00 0.00 0.00 0.00 6.97 0.00 0.04 0.03 0.04 0.10 0.17 17.95−0.09 −0.03 −0.05 −0.01 0.01 0.16 21.09 −0.04 −0.03 −0.01 0.02 0.06 0.2328.10 −0.12 −0.16 −0.10 −0.07 −0.04 0.19 35.10 −0.07 −0.10 −0.07 −0.02−0.02 0.28 48.99 −0.05 −0.08 −0.05 −0.02 0.00 0.36 59.89 −0.07 −0.11−0.06 −0.04 −0.01 0.45 A contains 1% of the UV absorber. B contains 0.5%of the UV absorber. C contains 0.25% of the UV absorber. D contains 0.2%of the UV absorber. E contains 0.1% of the UV absorber. F is a controlcontaining no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order A>D>B>C>E>>F. These data show that thenitroxide plus UV absorber plus polymer provides resistance to yellowingafter 168 hours of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order A>C>D=B>E>>F. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 77days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order B>A>C>D>E>F. These data show that the nitroxide plus UVabsorber plus polymer provides resistance to yellowing after 60 days ofdark aging.

EXAMPLE 44

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25%, 0.2%, 0.15%, 0.1% and 0.05% byweight of the hindered amine nitroxide Compound B, 0.5% by weight of thebenzotriazole UV absorber TINUVIN® 1130 and 0.5% by weight of polymerPTHF are compared for efficacy in preventing yellowing. The data arepresented on the three tables below respectively.

Time a b c d e f Accelerated Test Method 0.00 0.00 0.00 0.00 0.00 0.000.00 26.00 0.49 0.41 1.12 1.93 2.02 6.01 48.33 1.10 0.91 1.95 3.21 3.339.20 73.50 1.63 1.39 2.73 4.47 4.55 11.87 96.00 2.23 1.80 3.32 5.44 5.5914.00 119.83 2.64 2.31 4.13 6.63 6.65 15.98 144.83 3.16 2.76 4.81 7.707.64 17.94 167.67 3.76 3.36 5.63 8.85 8.82 19.87 191.00 4.25 3.73 6.159.86 9.64 21.07 216.42 5.20 4.73 7.58 11.69 11.18 23.66 Ambient TestMethod 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.99 −0.19 −0.10 −0.12 0.100.20 0.76 8.98 −0.17 0.06 0.01 0.37 0.61 1.98 16.00 −0.08 0.17 0.22 0.701.09 3.14 23.03 0.09 0.28 0.31 0.93 1.45 3.98 30.07 0.31 0.58 0.65 1.392.03 5.30 37.13 0.56 0.80 0.99 1.85 2.47 6.30 44.04 0.61 0.86 1.00 1.962.83 7.10 47.00 0.71 0.94 1.02 2.02 2.94 7.26 54.00 0.93 1.18 1.35 2.363.47 8.36 57.96 0.93 1.20 1.46 2.48 3.63 8.86 64.98 1.14 1.43 1.79 2.764.03 9.95 72.00 1.27 1.75 2.04 3.21 4.61 11.01 Dark Aging Test Method0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.02 0.03 0.03 0.06 0.04 0.07 0.1112.98 −0.06 −0.06 0.00 −0.01 0.02 0.21 16.15 −0.01 −0.01 0.03 0.03 0.070.28 23.15 −0.09 −0.12 −0.05 −0.07 0.02 0.25 30.15 −0.10 −0.08 −0.03−0.07 0.05 0.34 37.13 −0.06 −0.06 −0.01 −0.01 0.08 0.38 44.04 −0.09−0.06 −0.03 −0.02 0.07 0.42 54.94 −0.11 −0.07 −0.03 −0.05 0.08 0.4772.03 0.00 −0.04 0.00 −0.03 0.11 0.56 A contains 0.25% of the nitroxide.B contains 0.2% of the nitroxide. C contains 0.15% of the nitroxide. Dcontains 0.1% of the nitroxide. E contains 0.05% of the nitroxide. F isa control containing no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order B>A>C>D>E>>F. These data show that thenitroxide plus UV absorber plus polymer provides resistance to yellowingafter 216 hours of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order A>B>C>D>E>>F. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 72days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order B>D>C>A>E>>F. These data show that the nitroxide plus UVabsorber plus polymer provides resistance to yellowing after 72 days ofdark aging.

EXAMPLE 45

Using the accelerated test method; the ambient test method; and darkaging, BTMP handsheets containing 0.25% by weight of the hindered aminenitroxide Compound B, 0.5% by weight of the benzotriazole UV absorberTINUVIN® 1130 and 1%, 0.75%, 0.25% or 0.1% by weight of the polymer PTHFare compared for efficacy in preventing yellowing. The data arepresented on the three tables below respectively.

Time a b c d e Accelerated Test Method 0.00 0.00 9.00 0.00 0.00 0.0022.33 0.49 0.86 0.31 0.45 4.68 47.50 1.11 1.76 0.77 1.04 7.82 70.00 1.612.53 1.20 1.49 10.05 93.00 2.26 3.36 1.73 2.08 12.46 118.83 2.70 4.102.16 2.67 14.44 141.67 3.41 5.04 2.80 3.39 16.69 165.00 3.95 5.74 3.203.90 18.16 189.42 4.97 7.28 4.18 5.52 21.00 214.00 6.32 9.24 5.37 6.8624.13 Ambient Test Method 0.00 0.00 0.00 0.00 0.00 0.00 7.90 −0.21 0.13−0.20 −0.07 1.75 14.92 −0.10 0.32 −0.08 0.12 2.96 21.92 −0.05 0.43 −0.060.21 3.87 28.98 0.24 0.74 0.19 0.52 5.15 43.04 0.59 1.03 0.29 1.08 6.9745.91 0.69 1.08 0.35 0.99 7.13 52.88 0.90 1.40 0.55 1.26 8.23 56.92 0.901.46 0.59 1.34 8.74 63.90 1.12 1.78 0.85 1.71 9.77 Dark Aging TestMethod 0.00 0.00 0.00 0.00 0.00 0.00 0.94 0.04 0.03 0.02 0.02 0.04 11.92−0.03 −0.04 −0.06 −0.04 0.23 15.06 0.03 0.00 −0.01 0.01 0.33 22.07 −0.07−0.07 −0.09 −0.09 0.31 29.07 −0.04 −0.04 −0.08 −0.04 0.42 42.96 −0.03−0.04 −0.06 −0.05 0.49 53.85 −0.01 −0.04 −0.07 −0.05 0.61 70.96 0.060.01 −0.03 −0.04 0.76 A contains 1% of the polymer PTHF. B contains0.75% of the polymer PTHF. C contains 0.25% of the polymer PTHF. Dcontains 0.1% of the polymer PTHF. E is a control containing nostabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order C>A>D>B>>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 214hours of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order C>A>D>B>>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 64days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order D>C>B>A>>>E. These data show that the nitroxide plus UVabsorber plus polymer provides resistance to yellowing after 71 days ofdark aging.

EXAMPLE 46

Using the accelerated test method; the ambient test method; and darkaging, BCTMP Aspen handsheets containing 0.25% by weight of the hinderedamine nitroxide Compound B, 1%, 0.5% or 0% by weight of thebenzotriazole UV absorber TINUVIN® 1130 and 1%, 0.5% or 0% by weight ofthe polymer PTHF are compared for efficacy in preventing yellowing. Thedata are presented on the three tables below respectively.

Time a b c d e Accelerated Test Method 0.00 0.00 0.00 0.00 0.00 0.001.00 3.50 2.59 0.77 1.02 5.81 2.02 5.57 3.81 1.16 1.51 8.77 3.03 7.495.05 1.71 2.02 11.62 4.01 9.04 5.82 2.06 2.46 13.93 4.98 10.54 6.76 2.562.95 16.26 6.14 12.04 7.67 2.82 3.21 18.49 7.64 13.90 8.61 3.37 3.8121.64 8.24 14.60 8.76 3.54 3.95 22.42 Ambient Test Method 0.00 0.00 0.000.00 0.00 0.00 1.99 0.76 0.49 0.07 0.26 1.51 3.06 1.27 0.84 0.28 0.482.44 24.13 1.80 1.22 0.52 0.73 3.25 31.13 2.00 1.34 0.61 0.76 3.85 34.021.94 1.33 0.61 0.79 3.93 41.00 2.16 1.63 0.84 0.95 4.63 45.00 2.39 1.660.84 0.96 4.91 52.14 2.81 1.66 1.04 1.13 5.57 59.02 3.15 1.84 1.23 1.226.10 Dark Aging Test Method 0.00 0.00 0.00 0.00 0.00 0.00 9.17 −0.04−0.03 0.01 −0.02 0.01 16.16 0.03 0.01 0.07 0.04 0.03 23.13 0.09 0.080.12 0.08 0.10 30.06 0.07 0.03 0.10 0.03 0.05 40.94 0.06 0.04 0.11 0.050.05 58.04 0.11 0.28 0.32 0.28 0.29 A contains no UV absorber or nopolymer PTHF. B contains no UV absorber and 1% of the polymer PTHF. Ccontains of 1% of the UV absorber and no polymer PTHF. D contains 0.5%of the UV absorber and 0.5% of polymer PTHF. E is a control containingno stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order C>D>B>A>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 8days of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order C>D>B>A>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 59days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order A>B>D>E>C. These data show that the nitroxide plus UVabsorber plus polymer provides resistance to yellowing after 71 days ofdark aging.

EXAMPLE 47

Using the accelerated test method; the ambient test method; and darkaging, stone-ground wood (SGW) handsheets containing 0.25% by weight ofthe hindered amine nitroxide Compound B, 1%, 0.5% or 0% by weight of thebenzotriazole UV absorber TINUVIN® 1130 and 1%, 0.5% or 0% by weight ofthe polymer PTHF are compared for efficacy in preventing yellowing. Thedata are presented on the three tables below respectively.

Time a b c d e Accelerated Test Method 0.00 0.00 0.00 0.00 0.00 0.000.99 3.94 3.28 0.82 1.51 8.19 1.97 6.95 5.11 1.69 2.70 12.54 2.94 9.756.84 2.48 3.81 16.70 4.09 12.18 8.83 3.34 5.09 20.41 5.60 15.07 10.724.42 6.39 25.36 6.20 15.74 11.24 4.83 6.90 26.84 Ambient Test Method0.00 0.00 0.00 0.00 0.00 0.00 6.95 0.44 0.15 −0.25 −0.24 1.80 14.01 1.190.63 0.08 0.03 3.22 28.08 2.27 1.28 0.51 0.36 5.25 30.98 2.26 1.32 0.570.38 5.30 37.96 2.91 1.74 0.82 0.63 6.55 41.94 3.03 1.86 0.89 0.70 7.1348.99 3.64 2.12 1.21 0.83 8.30 55.98 4.12 2.40 1.44 1.01 9.15 Dark AgingTest Method 0.00 0.00 0.00 0.00 0.00 0.00 7.13 −0.08 −0.17 −0.06 −0.130.10 14.12 −0.0l −0.15 −0.01 −0.14 −0.02 21.08 0.16 0.02 0.10 0.00 0.1828.02 0.13 −0.02 0.09 −0.03 0.13 38.90 0.18 0.00 −0.03 −0.09 0.13 56.000.88 0.13 0.31 0.05 0.28 A contains no UV absorber or no polymer PTHF. Bcontains no UV absorber and 1% of the polymer PTHF. C contains of 1% ofthe UV absorber and no polymer PTHF. D contains 0.5% of the UV absorberand 0.5% of polymer PTHF. E is a control containing no stabilizeradditive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order C>D>B>A>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 6days of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order D>C>B>A>>E. These data show that the nitroxideplus UV absorber plus polymer provides resistance to yellowing after 56days of ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order D>B>E>C>A. These data show that the nitroxide plus UVabsorber plus polymer provides resistance to yellowing after 56 days ofdark aging.

EXAMPLE 48

Using the accelerated test method; the ambient test method; and darkaging, BTMP paper loadings with 0.25%, 0.2%, 0.15%, 0.1% and 0.05% byweight of hindered amine nitroxide Compound B and 0.5% by weight ofCompound LL are compared for efficacy in preventing yellowing on aging.The data are presented on the three tables below respectively.

Time a b c d e f g h Accelerated Test Method 0.00 0.00 0.00 0.00 0.000.00 0.00 0.00 0.00 24.67 2.94 2.72 3.19 3.46 4.29 4.76 6.70 6.48 48.255.79 5.16 5.68 6.06 7.46 8.16 10.98 10.98 71.75 7.60 7.25 7.93 8.3110.03 11.02 14.43 14.37 97.08 9.13 8.83 9.60 10.13 11.85 13.14 16.9817.00 120.25 10.76 10.55 11.21 11.72 13.58 15.01 19.31 19.34 168.2514.63 14.71 15.17 15.52 18.08 19.76 25.10 25.36 Ambient Test Method 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8.01 0.39 0.21 0.54 0.50 0.681.13 1.91 2.05 15.03 0.62 0.41 0.81 0.80 1.05 1.67 2.80 3.02 22.05 1.190.89 1.30 1.28 1.62 2.44 3.92 4.31 29.14 1.74 1.25 1.74 1.78 2.13 3.174.88 5.38 36.14 2.07 1.45 2.00 2.00 2.48 3.56 5.65 6.25 39.01 2.03 1.472.01 2.06 2.50 3.60 5.75 6.46 46.01 2.46 1.98 2.53 2.53 3.11 4.42 6.827.62 50.01 2.62 2.04 2.67 2.71 3.31 4.74 7.28 8.10 56.99 3.06 2.40 3.093.11 3.71 5.33 8.24 9.17 64.01 3.36 2.80 3.46 3.42 4.25 5.94 9.19 10.03Dark Aging Test Method 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 8.160.09 −0.06 0.02 0.08 0.02 0.05 0.13 0.17 15.17 −0.08 −0.21 −0.11 −0.05−0.07 −0.05 0.10 0.18 22.18 −0.13 −0.22 −0.17 −0.11 −0.09 −0.07 0.130.30 29.14 0.01 −0.16 0.01 0.06 0.01 0.06 0.29 0.40 36.07 0.00 −0.22−0.05 0.02 −0.02 0.03 0.27 0.40 46.95 −0.07 −0.21 −0.05 0.01 −0.03 0.040.32 0.49 A contains 0.25% nitroxide and 0.5% brightner. B contains 0.2%nitroxide and no brightner. C contains 0.25% nitroxide and 0.5%brightner. D contains 0.15% nitroxide and 0.5% brightner. E contains0.1% nitroxide and 0.5% brightner. F contains 0.05% nitroxide and 0.5%brightner. G is a control containing no nitroxide and 0.5% brightner. His a control containing no stabilizer additive.

During accelerated photoaging, inspection of the data on the table showsin best to poorest order A>B>C>D>E>F>>G=H. These data show that thenitroxide plus brightner provides resistance to yellowing after 168hours of accelerated photoaging.

During ambient photoaging, inspection of the data on the table shows inbest to poorest order B>A=C=D>E>F>G>H. These data show that thenitroxide plus brightner provides resistance to yellowing after 64 daysof ambient photoaging.

During dark aging, inspection of the data on the table shows in best topoorest order B>C>A>E>D>F>G>H. These data show that the nitroxide plusbrightner provides resistance to yellowing after 47 days of dark aging.

EXAMPLE 49

Using the dark aging method, BTMP handsheets are allowed to sit in thedark for 10 days before treatment with 0.05% by weight of nitroxideCompound B. The sheets are then dark aged for a period of 72 days. TheISO brightness data are given on the table below.

Days e f −10 78.11 78.22 0 77.94 77.48 2.02 77.71 77.14 12.98 77.8976.85 16.15 77.72 76.65 23.15 77.87 76.75 30.15 77.8 76.48 37.13 77.6876.37 44.04 77.74 76.28 54.94 77.7 76.13 72.03 77.6 75.89 E contains0.05% nitroxide. F is a control containing no stabilizer additive.

The nitroxide provides the good ISO brightness values after the 72 dayperiod of dark aging.

EXAMPLE 50 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.5% by weight of Compound S and 0.5% byweight of Compound A and Compound FF:

Time S, A S, FF S A FF Control in days PC Number 0 0 0 0 0 0 0 0.78 0.14−0.23 1.93 0.7 0.67 3.26 1.75 0.38 −0.32 3.77 1.12 1.09 6.19 2.75 0.85−0.19 5.8 1.93 1.86 9.16 3.77 1.25 −0.14 7.62 2.51 2.45 11.6 4.77 1.54−0.22 9.48 3.19 3.07 13.8 5.75 1.87 −0.07 10.9 3.74 3.59 15.83 6.78 2.16−0.13 11.87 4.22 4.07 16.97

Inspection of the data reveals that hydroxylamine citrate salt are moreeffective in inhibiting yellowing than the hydroxylamine and incombination with a UVA superior results are achieved with the citratesalt.

EXAMPLE 51 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A and with 1%by weight of the sulfur containing inhibitors:

2-(2′-methoxyethoxy)-ethanethiol;

2,2′-oxydiethanethiol;

1-thioglycerol;

sodium thioglycolate;

thiolactic acid;

sodium thiolactate;

β-mercaptopropionic acid;

sodium β-mercaptopropionate;

glycol dimercaptoacetate;

glycol dimercaptopropionate;

polyethylene glycol dimercaptoacetate;

polyethylene glycol dimercaptopropionate;

pentaerythritol tetrathioglycolate;

trimethylol propane tri-(3-mercaptopropionate);

polymethylene sulfide;

disodium methylene bis thiopropionate;

3,3′-thiodipropionic acid;

dithiothreitol.

The sheets treated with a combination of hydroxylamine and sulfurcontaining compounds exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when combinations of hydroxylamine and sulfur containingcompounds are used.

EXAMPLE 52 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound FF and with 1%by weight of the sulfur containing inhibitors:

2-(2′-methoxyethoxy)-ethanethiol;

2,2′-oxydiethanethiol;

1-thioglycerol;

sodium thioglycolate;

thiolactic acid;

sodium thiolactate;

β-mercaptopropionic acid;

sodium β-mercaptopropionate;

glycol dimercaptoacetate;

glycol dimercaptopropionate;

polyethylene glycol dimercaptoacetate;

polyethylene glycol dimercaptopropionate;

pentaerythritol tetrathioglycolate;

trimethylol propane tri-(3-mercaptopropionate);

polymethylene sulfide;

disodium methylene bis thiopropionate;

3,3′-thiodipropionic acid;

dithiothreitol.

The sheets treated with a combination of hydroxylamine salt and sulfurcontaining compounds exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when combinations of hydroxylamine salt and sulfurcontaining compounds are used.

EXAMPLE 53 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound B and with 1%by weight of the sulfur containing inhibitors Compounds GG, HH and II:

Time in B, GG B, HH B, II GG HH II control Days PC Number 0 0 0 0 0 0 00 0.92 1.1 1.25 1.1 2.92 3.65 2.55 3.94 1.88 2.4 2.32 2.09 5.9 6.45 4.936.91 3.9 5.33 4.36 3.98 11.88 11.48 9.81 12.15 5 7.31 5.59 5.13 15.5614.26 12.86 14.84 5.98 9.37 6.88 6.32 18.55 16.58 15.5 17.13 6.95 11.328.06 7.37 21.3 18.51 17.75 18.93 7.92 13.34 9.17 8.55 24.39 20.74 20.4321.43 8.88 15.1 10.34 9.72 27.33 22.74 22.9 23.55

The sheets treated with a combination of nitroxide and sulfur containingcompounds exhibit substantial inhibition to yellowing compared to theuntreated control sheet and illustrate the performance enhancement whencombinations of nitroxides and sulfur containing compounds are used.Inspection of the data reveals that Compound HH and II are particularlyeffective when combined with a nitroxide.

EXAMPLE 54 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A, 0.5% ofCompound R and with 1% by weight of the sulfur containing inhibitors:

2-(2′-methoxyethoxy)-ethanethiol;

2,2′-oxydiethanethiol;

1-thioglycerol;

sodium thioglycolate;

thiolactic acid;

sodium thiolactate;

β-mercaptopropionic acid;

sodium β-mercaptopropionate;

glycol dimercaptoacetate;

glycol dimercaptopropionate;

polyethylene glycol dimercaptoacetate;

polyethylene glycol dimercaptopropionate;

pentaerythritol tetrathioglycolate;

trimethylol propane tri-(3-mercaptopropionate);

polymethylene sulfide;

disodium methylene bis thiopropionate;

3,3′-thiodipropionic acid;

dithiothreitol.

The sheets treated with a combination of hydroxylamine, UVA and sulfurcontaining compounds exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when combinations of hydroxylamine, UVA and sulfurcontaining compounds are used.

EXAMPLE 56 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound FF, 0.5% ofCompound R and with 1% by weight of the sulfur containing inhibitors:

2-(2′-methoxyethoxy)-ethanethiol;

2,2′-oxydiethanethiol;

1-thioglycerol;

sodium thioglycolate;

thiolactic acid;

sodium thiolactate;

β-mercaptopropionic acid;

sodium β-mercaptopropionate;

glycol dimercaptoacetate;

glycol dimercaptopropionate;

polyethylene glycol dimercaptoacetate;

polyethylene glycol dimercaptopropionate;

pentaerythritol tetrathioglycolate;

trimethylol propane tri-(3-mercaptopropionate);

polymethylene sulfide;

disodium methylene bis thiopropionate;

3,3′-thiodipropionic acid;

dithiothreitol.

The sheets treated with a combination of hydroxylamine salt, UVA andsulfur containing compounds exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when combinations of hydroxylamine salt, UVA and sulfurcontaining compounds are used.

EXAMPLE 57 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound B, 0.5% ofCompound R and with 1% by weight of the sulfur containing inhibitorsCompounds GG, HH and II:

Time R, B, R, B, R, B, in R B GG HH II R, GG R, HH R, II control Days PCNumber 0 0 0 0 0 0 0 0 0 0.92 1.62 1.52 0.97 0.48 0.5 1.58 1.92 1.513.94 1.88 3.05 3 2.08 1.1 1.2 3.23 3.56 3.08 6.91 3.9 5.8 5.99 4.33 2.142.55 6.65 6.75 6.35 12.15 5 7.47 7.58 5.82 2.99 3.65 9.12 8.93 8.6314.84 5.98 9.07 9 7.26 3.82 4.7 11.17 10.65 10.59 17.13 6.95 10.28 10.358.43 4.58 5.78 12.99 12.25 12.36 18.93 7.92 11.58 11.72 10.03 5.38 6.7714.95 14.05 14.36 21.43 8.88 12.9 12.88 11.21 6.13 7.89 17.25 15.9716.12 23.55

The sheets treated with a combination of nitroxide, UVA and sulfurcontaining compounds exhibit substantial inhibition to yellowingcompared to the untreated control sheet and illustrate the performanceenhancement when combinations of nitroxides, UVA and sulfur containingcompounds are used. Inspection of the data reveals that Compound HH andII are particularly effective when combined with a nitroxide and UVA.

EXAMPLE 58 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A and with 1%by weight of the following metal salts:

MgSO₄

MnSO₄

ZnSO₄

The sheets treated with a combination of hydroxylamine and metal saltexhibit substantial inhibition to yellowing compared to the untreatedcontrol sheet and illustrate the performance enhancement whencombinations of hydroxylamine and metal salt are used.

EXAMPLE 59 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound B and with 1%by weight of the following metal salts:

MgSO₄

MnSO₄

ZnSO₄

The sheets treated with a combination of nitroxide and metal saltexhibit substantial inhibition to yellowing compared to the untreatedcontrol sheet and illustrate the performance enhancement whencombinations of nitroxide and metal salt are used.

EXAMPLE 60 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound A and with 1%by weight of the diene compounds:

1-methoxy-1,3-cyclohexadiene;

1-methoxy-1,4-cyclohexadiene;

2,4-hexadienoic acid;

trans, trans-2,4-hexadien-1-ol.

The sheets treated with a combination of hydroxylamine and dienecompound exhibit substantial inhibition to yellowing compared to theuntreated control sheet and illustrate the performance enhancement whencombinations of hydroxylamine and diene compound are used.

EXAMPLE 61 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound B and with 1%by weight of the following diene compounds:

1-methoxy-1,3-cyclohexadiene;

1-methoxy-1,4-cyclohexadiene;

2,4-hexadienoic acid;

trans, trans-2,4-hexadien-1-ol.

The sheets treated with a combination of nitroxide and diene compoundexhibit substantial inhibition to yellowing compared to the untreatedcontrol sheet and illustrate the performance enhancement whencombinations of nitroxide and compounds are used.

EXAMPLE 62 Accelerated Yellowing with High Intensity Lamps

BTMP sheets are treated with 0.25% by weight of Compound FF and with 1%by weight of the following diene compounds:

1-methoxy-1,3-cyclohexadiene;

1-methoxy-1,4-cyclohexadiene;

2,4-hexadienoic acid;

trans, trans-2,4-hexadien-1-ol.

The sheets treated with a combination of hydroxylamine salt and dienecompound exhibit substantial inhibition to yellowing compared to theuntreated control sheet and illustrate the performance enhancement whencombinations of hydroxylamine salt and compounds are used.

EXAMPLE 63 1-Oxyl-2,2,6,6-tetramethyl-4-glycidyloxypiperidine

A vigorously stirred two phase solution of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine, epichlorohydrin,tetrabutylammonium bromide in 50% aqueous sodium hydroxide and tolueneis reacted together. The organic phase is dried over anhydrous magnesiumsulfate and concentrated to yield the title compound as a low meltingred solid after column chromatography.

EXAMPLE 641-Oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxa-6-trimethylammmoniumhexyloxy)piperidineChloride

The title compound is prepared by reacting the glycidyloxy compound ofExample 1 with choline chloride [(2-hydroxyethyl)trimethylammoniumchloride].

EXAMPLE 651-Oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-trimethylammoniumpropoxy)piperidineChloride

To 25 mL of 0.4 molar aqueous trimethylammonium hydroxide (0.01 mol) isadded 2.28 g (0.01 mol) of1-oxyl-2,2,6,6-tetramethyl4-glycidyloxypiperidine. The mixture isstirred at ambient temperature for 16 hours. The solution is thenneutralized with one equivalent of hydrochloric acid, washed twice with50 mL of ethyl acetate and concentrated under reduced pressure. Theresulting red oil is purified by column chromatography yielding 1.0 g ofthe title compound as a red oil.

EXAMPLE 661-Oxyl-2,2,6,6-tetramethyl-4-{2-hydroxy-3-[di(2-hydroxyethyl)amino]propoxy}piperidine

A solution of 2.28 g (0.01 mol) of1-oxyl-2,2,6,6-tetramethyl-4-glycidyloxypiperidine and 1.05 g (0.01 mol)of diethanolamine in 25 mL of water is stirred at ambient temperaturefor 16 hours. The solution is then extracted with methylene chloride.The methylene chloride extract is dried over anhydrous magnesiumsulfate, filter and concentrated. The crude reaction product is purifiedby column chromatography to afford 1.0 g of the title compound as a redoil.

EXAMPLE 671-Oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-dimethylaminopropoxy)piperidine

A mixture of 10.0 g (0.044 mol) of1-oxyl-2,2,6,6-tetramethyl-4-glycidyloxypiperidine and 10 mL of 40% (ca.0.091 mol) of dimethylamine (w/w) is dissolved in 100 mL of water andthen stirred for 16 hours at ambient temperature. Water is then removedby vacuum distillation to leave 10 g of the title compound as a red oil.

EXAMPLE 681-Oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-diethylaminopropoxy)piperidine

The title compound is prepared according to the procedure of Example 5when the dimethylamine is replaced with an equivalent amount ofdiethylamine. The product is purified by column chromatography and isisolated as a red oil.

EXAMPLE 69N,N′-Dimethyl-N,N′-bis-[3-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxy)-2-hydroxypropyl]hexamethylenediamine

The title compound is prepared according to the procedure of Example 4replacing diethanolamine with an equivalent amount ofN,N′dimethylhexamethylenediamine. The product is purified by columnchromatography and is isolated as a red oil.

EXAMPLE 70N,N,N′,N′-Tetramethyl-N,N′-bis-[3-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxy)-2-hydroxypropyl]-hexamethylenediammoniumDibromide

A solution of 3.0 g (0.011 mol) of the compound of Example 5 and 0.89 g(0.0036 mol) of dibromohexane om 25 mL of absolute ethanol is refluxedfor 16 hours. The resultant solution is concentrated under reducedpressure and the residue is washed thrice with 20 mL of ethyl acetateand then dried under vacuum. The title compound is obtained in a yieldof 3.0 g as a red solid.

EXAMPLE 711-Oxyl-2,2,6,6-tetramethyl-4-[2-hydroxy-3-(N,N-dimethyl-N-propylammonium)propoxy]piperidineChloride

The title compound is prepared according to the procedure of Example 8by replacing 1,6-dibromohexane with an equivalent amount of1-bromopropane. The title compound is isolated as a red oil.

EXAMPLE 72 Ethyl 1-Oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxyacetate

To a solution of 3.0 g (17 mmol) of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine in 25 mL of anhydroustetrahydrofuran is added 0.48 g (20 mmol) of sodium hydride. Thereaction mixture is stirred under a blanket of nitrogen for one hour.The mixture is then chilled to 0° C. amd 2.9 g (17 mmol) of ethylbromoacetate is added dropwise. After the addition, the reaction mixtureis stirred for an additional 30 minutes during which time a precipitateforms. The mixture is filtered and the solvent is removed under reducedpressure. The title compound is isolated after column chromatography asan orange solid melting at 41-43° C.

EXAMPLE 73 1-Oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetic Acid

To a solution of 0.2 g of sodium hydroxide in 20 mL of 1:1water:methanol is added 1.0 g (39 mmol) of the compound of Example 10.The mixture is stirred for one hour and then carefully acidified with 1%aqueous hydrochloric acid. The resultant mixture is extracted with ethylacetate. The organic extract is dried over anhydrous magnesium sulfateand concentrated under reduced pressure to afford the title compound asan orange solid.

EXAMPLE 74 Sodium 1-Oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetate

To a solution of 1.0 g (4.3 mmol) of the compound of Example 11dissolved in 20 mL of water is added 0.17 g (4.3 mmol) of sodiumhydroxide. The solution is stirred for one hour and the water is thenremoved by vacuum distillation to afford the title compound as an orangesolid.

EXAMPLE 75 1-Oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetic AcidCholine Ester

The title compound is prepared by reacting the acid of Example 11 withcholine chloride [(2-hydroxyethyl)trimethylammonium chloride].

EXAMPLE 76 1-Hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium Chloride

67 mL of isopropanol is cooled to 0° C. and saturated with HCl gas. Thissolution is added dropwise to a mechanically stirred solution of 50 g(0.29 mol) 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine in 130 mL ofisopropanol, maintaining a reaction temperature of about 20° C. byoccasionally cooling with an ice bath. The HCl salt is vacuum filteredand washed with isopropanol, giving a pale yellow solid. 5.0 g of thiscrude product is recrystallized from 100 mL isopropanol affording 3 g ofa white crystalline solid, mp>260° C.

Elemental Analysis

Calc. Found % C 51.55 51.30 % H 9.61 9.70 % N 6.68 6.42 % Cl 16.91 16.83

EXAMPLE 77 1-Hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium Acetate

5.0 g (0.029 mol) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine and2.0 g (0.033 mol) acetic acid are recrystallized from 50 mL ofisopropanol, yielding 4.0 g of the desired hydroxylamine salt as a whitecrystalline solid, mp 140-143° C.

Elemental Analysis

Calc. Found % C 56.63 56.78 % H 9.94 10.13 % N 6.00 6.07

EXAMPLE 78 1-Hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium Bisulfate

5.0 g (0.029 mol) 1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidine and3.0 g (0.031 mol) sulfuric acid are recrystallized from 50 mL ofisopropanol, yielding 3.0 g of the desired hydroxylamine salt as a whitecrystalline solid, mp 238-241° C.

Elemental Analysis

Calc. Found % C 39.99 40.06 % H 7.46 8.06 % N 5.18 5.11 % S 11.86 11.87

EXAMPLE 79 1-Hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidiniumBisulfate

2.6 ml of concentrated sulfuric acid is added dropwise to a solution of10.0 g (46.9 mmol) 1-oxyl-2,2,6,6-tetramethyl-4-acetamidopiperidine in50 ml isopropanol. After 48 hrs the resulting white solid is collectedby filtration, washed with isopropanol and dried under vacuum, mp 198°C.

Elemental Analysis

Calc. Found % C 42.28 42.23 % H 7.76 7.76 % N 8.97 8.85

EXAMPLE 80Bis-(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)Oxalate

To a glass 0.5 L reaction bottle are added 10.0 g (58 mmol) of C, 5.22 g(58 mmol) oxalic acid, 200 mg 5% Pt on C and 100 mL water. Catalytichydrogenation is carried out at 50 psi for 30 minutes at roomtemperature. Catalyst is removed by vacuum filtration with Celite. Wateris removed by distillation under reduced pressure, giving a colorlesssolid. The crude product is recrystallized from 100 mL isopropanolaffording 3.5 g of the product as a white crystalline solid, mp 244° C.

Elemental Analysis

Calc. Found % C 55.03 54.69 % H 9.24 9.49 % N 6.42 6.32

EXAMPLE 81Tris-(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)Citrate

To a glass 0.5 L reaction bottle are added 20.0 g (116 mmol) of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine, 7.39 g (38.5 mmol)citric acid, 200 mg 5% Pt on C and 100 mL water. Catalytic hydrogenationis carried out at 50 psi for 30 minutes at room temperature. Catalyst isremoved by filtration through a pad of Celite. The aqueous salt solutionhas a pH of 5.56. Removal of water yields the product as a hygroscopicglassy solid.

EXAMPLE 82Bis-(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)Citrate

To a glass 0.5 L reaction bottle are added 20.0 g (116 mmol) of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine, 11.12 g (58 mmol) citricacid, 200 mg 5% Pt on C and 100 mL water. Catalytic hydrogenation iscarried out at 50 psi for 30 minutes at room temperature. Catalyst isremoved by filtration through a pad of Celite. The aqueous salt solutionhas a pH of 4.39. Removal of water yields the product as a hygroscopicglassy solid.

EXAMPLE 83 1-Hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium Citrate

To a glass 0.5 L reaction bottle are added 20.0 g (116 mmol) of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine, 22.2 g (116 mmol) citricacid, 200 mg 5% Pt on C and 100 mL water. Catalytic hydrogenation iscarried out at 50 psi for 30 minutes at room temperature. Catalyst isremoved by filtration through a pad of Celite. The aqueous salt solutionhas a pH of 3.30. Removal of water yields the product as a hygroscopicglassy solid.

EXAMPLE 84Bis-(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium)Sulfate

To a glass 0.5 L reaction bottle are added 10.0 g (58 mmol) of1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine, 2.85 g (29 mmol)sulfuric acid, 200 mg 5% Pt on C and 100 mL water. Catalytichydrogenation is carried out at 50 psi for 30 minutes at roomtemperature. Catalyst is removed by filtration through a pad of Celite.Removal of water yields the product as an pale yellow solid.

What is claimed is:
 1. A hindered nitroxide compound of formula IV, V,VI, VII or VIII

wherein n is 2 to 3, G₁ is hydrogen, methyl, ethyl, butyl or benzyl, Xis inorganic or organic anion, when x is 1, R₁ and R₂ are independentlyalkyl of 1 to 18 carbon atoms, said alkyl interrupted by one to fiveoxygen atoms, said alkyl substituted by 1 to 5 hydroxyl groups or saidalkyl both interrupted b said oxygen atoms and substituted by saidhydroxyl groups; cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 15carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted byone to three alkyl of 1 to 8 carbon atoms, or R₁ is also hydrogen, or R₁and R₂ are together tetramethyl, pentamethylene, hexamethylene or3-oxapentamethylene, when x is 2, R₁ is hydrogen, alkyl of 1 to 8 carbonatoms, said alkyl interrupted by one or two oxygen atoms and substitutedby a hydroxyl group, R₂ is alkylene of 2 to 18 carbon atoms, saidalkylene interrupted by one to five oxygen atoms, said alkylenesubstituted by 1 to 5 hydroxyl groups or said alkylene both interruptedby said oxygen atoms and substituted by said hydroxyl groups; o-, m- orp-phenylene or said phenylene substituted by one or two alkyl of 1 to 4carbon atoms, or R₂ is -(CH₂)_(k)O[(CH₂)_(k)O]_(h)(CH₂)_(k)-where k is 2to 4 and h is 1 to 40, or R₁ and R₂ together with the two N atoms towhich they are attached are piperazin-1,4-diyl, when x is 3, R₁ ishydrogen, R₂ is alkylene of 4 to 8 carbon atoms interrupted by onenitrogen atom, R₁ is hydrogen, R₂ is alkylene of 6 to 12 carbon atomsinterrupted by two nitrogen atoms, R₃ is hydrogen, alkyl of 1 to 8carbon atoms, said alkyl interrupted by one or two oxygen atoms, saidalkyl substituted by b hydroxyl group, or both interrupted by one or twooxygen atoms and substituted by a hydroxyl group, p is 2 or 3, and Q isan alkali metal salt, ammonium or N⁺(G₁)₄.
 2. A compound according toclaim 1 wherein X is phosphate, phosphonate, carbonate, bicarbonate,nitrate, chloride, bromide, bisulfite, sulfite, bisulfate, sulfate,borate, formate, acetate, gluconate, benzoate, citrate, oxalate,tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate,gluconate, malate, mandelate, tiglate, ascorbate, polymethacrylate, acarboxylate of nitrilotriacetic acid,hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraaceticacid or of diethylenetriaminepentaacetic acid, adiethylenetriaminepentamethylenephosphonate, an alkylsulfonate or anarylsulfonate.
 3. A compound according to claim 1 where in the compoundsof formulas IV to VIII n is 2; G₁ is hydrogen or methyl; X is chloro orbromo; x is 1 or 2, R₁ and R₂ are independently alkyl of 1 to 8 carbonatoms, said alkyl interrupted by one or two oxygen atoms, said alkylsubstituted by a hydroxyl group, or said alkyl both interrupted by oneor two oxygen atoms and substituted by a hydroxyl group, or R₁ ishydrogen; or R₁ and R₂ together are 3-xapentamethylene; R₃ is hydrogenor alkyl of 1 to 2 carbon atoms, or said alkyl substituted by a hydroxylgroup, p is 2, m is 1, and Q is Na⁺, NH₄ ⁺ or N(CH₃)₄ ⁺.
 4. A compoundaccording to claim 1 which is (a)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-4-oxa-6-trimethylammmoniumhexyloxy)piperidinechloride; (b)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-trimethylammoniumpropoxy)peperidinechloride; (c)1-oxyl-2,2,6,6-tetramethyl-4-{2-hydroxy-3-[di(2-hydroxyethyl)amino]propoxy}piperidine;(d)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-dimethylaminopropoxy)piperidine;(e)1-oxyl-2,2,6,6-tetramethyl-4-(2-hydroxy-3-diethylaminoproipoxy)piperidine;(f)N,N'-diethyl-N,N'-bis-[3-(1-oxyl-2,2,6,6-tetramethyl-piperidin-4-yloxy)-2-hydroxypropyl]-hexamethylenediamine;(g)N,N,N',N'-tetramethyl-N,N'-bis-[3-(1-oxyl-2,2,6,6-tetramethypiperidin-4-yloxy)-2-hydroxy-propyl]-hexamethylenediammoniumdibromide; (h)1-oxyl-2,2,6,6-tetramethyl-4-[2-hydroxy-3-(N,N-dimethyl-N-propylammonium)propoxy]-piperidinechoride; (i) sodium 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetate;or (j) 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yloxyacetic acid, cholineester.
 5. A hindered hydroxylamine salt of formula A*, D*, X*, Y*, Z*,AA*, BB*, CC* or DD*

wherein R is hydrogen, in formula A* n is 1 and R₁ is hydrogen or alkylof 1 to 4 carbon atoms, in formula D* y is 1, R₁₀ is hydrogen or methyl,R₁₂ is alkyl of 1 to 4 carbon atoms, X is phosphate, phosphonate,carbonate, bicarbonate, nitrate, chloride, bomide, bisulfite, sulfite,bisulfate, sulfate, borate, formate, acetate, benzoate, citrate,oxalate, tartrate, acrylate, polyacrylate, fumarate, maleate, itaconate,glycolate, malate, mandelate, tiglate, gluconate, ascorbate,polymethacrylate, a carboxylate of nitrilotriacetic acid,hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraaceticacid or of diethylenetriaminepentaacetic acid, adiethylenetriaminepentamethylenephosphonate, an alkylsulfonate or anarylsulfonate and where the total charge of cations h is equal to thetotal charge of anions j, in formulas X* to DD* n is 2 to 3, G₁ ishydrogen, methyl, ethyl, butyl or benzyl, m is 1 to 4, x is 1 to 4, whenx is 1, R₁ and R₂ are independently alkyl of 1 to 18 carbon atoms, saidalkyl interrupted by one to five oxygen atoms, said alkyl substituted by1 to 5 hyddroxyl groups or said alkyl both interrupted by said oxygenatoms and substituted by said hydroxyl groups; cycloalkyl of 5 to 12carbon atoms, aralkyl of 7 to 15 carbon atoms, aryl of 6 to 10 carbonatoms or said aryl substituted by one to three alkyl of 1 to 8 carbonatoms, or R₁ is also hydrogen, or R₁ and R₂ are together tetramethylene,pentamethylene, hexamethylene or 3-oxapentamethylene, when x is 2, R₁ ishydrogen, alkyl of 1 to 8 carbon atoms, said alkyl interrupted by one ortwo oxygen atoms, said alkyl substituted by a hydroxyl group, or saidalkyl both interrupted by one or two oxygen atoms and substituted by ahydroxyl group, R₂ is alkylene of 2 to 18 carbon atoms, said alkyleneinterrupted by one to five oxygen atoms, said alkylene substituted by 1to 5 hydroxyl groups or said alkylene both interrupted by said oxygenatoms and substituted by said hydroxyl groups; o-, m- or p-phenylene orsaid phenylene substituted by one or two alkyl of 1 to 4 carbon atoms,or R₂ is -(CH₂)_(k)O[(CH₂)_(k)O]_(h)(CH₂)-where k is 2 to 4 and h is 1to 40, or R₁ and R₂ together with the two N atoms to which they areattached are piperazin-1,4-diyl, when x is 3, R₁ is hydrogen, R₂ isalkylene of 4 to 8 carbon atoms interrupted by one nitrogen atom, when xis 4, R₁ is hydrogen, R₂ is alkylene of 6 to 12 carbon atoms interruptedby two nitrogen atoms, R₃ is hydrogen, alkyl of 1 to 8 carbon atoms,said alkyl interrupted by one or two oxygen atoms, said alkylsubstituted by a hydroxyl group, or both interrupted by one or twooxygen atoms and substituted by a hydroxyl group, p is 2 or 3 and Q isan alkali metal salt, ammonium or N⁺(G₁)₄, in formula DD and DD* when mis 2, G is -(CH₂CHR-O)_(r)CH₂CHR-, where r is 0 to 3, and R is hydrogenor methyl and when m is 3, G is glyceryl, with the proviso that informula A* when R₁ is hydrogen, X is not chloride or bisulfate, and whenin formula D* when R₁₀ is hydrogen and R₁₂ is methyl, X is not chlorideor bisulfate.
 6. A hydroxylamine salt according to claim 5 wherein X ischloride, bisulfate, ascorbate, bisulfite, sulfate, nitrate, acetate,citrate or a carboxylate of ethylenediaminetetraacetic acid ordiethylenetriaminepentaacetic acid.
 7. A hydroxylamine salt according toclaim 6 wherein X is bisulfate or citrate.
 8. A hydroxylamine saltaccording to claim 5 which is (a)1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium citrate; (b)bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate; (c)tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) citrate; (d)1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA; (e)bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA; (f)tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA; (g)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA; (h)pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium DTPA; (i)1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium EDTA; (j)bis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA; (k)tris(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA; (l)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA; (m)1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium citrate; (n)bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) citrate; (o)tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) citrate; (p)1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium DTPA; (q)bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA; (r)tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA; (s)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA; (t)pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) DTPA; (u)1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium EDTA; (v)bis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA; (w)tris(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA; (x)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidinium) EDTA; (y)1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium citrate; (z)bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) citrate; (aa)tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) citrate;(bb) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium DTPA; (cc)bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) DTPA; (dd)tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) DTPA; (ee)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) DTPA;(ff) pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium)DTPA; (gg) 1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium EDTA;(hh) bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) EDTA;(ii) tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetamidopiperidinium) EDTA;(jj) tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-hydroxypiperidinium) EDTA;(kk) 1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium citrate; (ll)bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) citrate; (mm)tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) citrate; (nn)1-hydroxy-2,3,6,6-tetramethyl-4-acetoxypiperidinium DTPA; (oo)bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA; (pp)tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA; (qq)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA; (rr)pentakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) DTPA; (ss)1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium EDTA; (tt)bis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA; (uu)tris(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA or (vv)tetrakis(1-hydroxy-2,2,6,6-tetramethyl-4-acetoxypiperidinium) EDTA.